English

• 1.   Introduction

  Due to the important building blocks in various compounds of agrochemicals and pharmaceuticals, ^[1] tetrahydroquinazoline derivatives encountered in a wide range of molecular targeted drugs, such as anti-cancer, anti-malaria, anti-inflammatory, and bactericidal agents.^[2] Therefore, considerable effort has been devoted to the development of effective approaches to the establishment of tetrahydroquinazoline derivatives. In recent years, different synthetic protocols for tetrahydroquinazoline derivatives have been developed using Bronsted acid, ^[3] p-toluenesulfonic acid (p-TSA), ^[4] iodine, ^[5] tin(Ⅱ) chloride dehydrate, ^[6] triphenylphosphine gold(I) triflate, ^[7] iron, ^[8] copper(Ⅱ) acetate monohydrate, ^[9] potassium carbonate, ^[10] acetic acid, ^[11] Oxone, ^[12] sodium acetate, ^[13] and sodium tetrahydroborate^[14] as catalysts. These protocols have greatly improved and enriched access to tetrahydroquinazoline derivatives. However, many of these methods are not fully satisfactory in terms of operational simplicity and mild reaction conditions, due to the multi-step process, excessive oxidants, and the requirement of reagents which are irritant and environment-unfriendly. Therefore, the exploitation of high- efficiency, environmentally-benign, and low-cost alternatives for the tetrahydroquinazolines synthesis remains challenges.

  As efficient, safe and selective catalysts, enzymes have aroused much attention in the agricultural, industrial production.^[15] Owing to high stability, selectivity and non- natural activity, hydrolases undoubtedly play a vital role among many types of enzymes, ^[16] which have been applied in different types of organic transformations, such as Gewald, ^[17] aldol, ^[18] retro-Claisen reaction, ^[19] Mannich, ^[20] and Friedländer reactions.^[21] However, to the best of our knowledge, enzyme-catalyzed synthesis of tetrahydroquinazoline between 2-aminobenzaldehyde (Ⅰ) and aromatic amine (Ⅱ) has never been reported. Herein, we report a mild and simple method for the synthesis of tetrahydroquinazoline derivatives from 2-aminobenzaldehydes (Ⅰ) and aromatic amines (Ⅱ) in which up to 94% yields were achieved using green hydrolase, pepsin, as biocatalyst (Scheme 1).

  Scheme 1

  

  Scheme 1.  Pepsin-catalyzed cyclocondensation of 2-aminoben- zaldehyde and aromatic amine

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  2.   Results and discussion

  The conditions for the reaction between 2-(1-pyrroli- dinyl)benzaldehyde (Ⅰ1) and aniline (Ⅱ1) in ethanol were initially examined. In the absence of pepsin, no detectable product was obtained in 36 h (Table 1, Entry 11). Some hydrolases for the catalysis of the model reaction were then investigated (Table 1). The highest yield (23%) was achieved using pepsin from porcine gastric mucosa (Table 1, Entry 5). In addition, both α-chymotrypsin (Table 1, Entry 1) and trypsin (Table 1, Entry 6) exhibited similar catalytic activity toward this transformation. Nevertheless, other enzymes demonstrated no catalytic ability. Finally, inactivated pepsin (Table 1, Entry 9) and non-enzyme protein bovine serum albumin (BSA) (Table 1, Entry 10) were used in the reaction, respectively, and no product was obtained. When no enzyme was used in the cyclization, no product was observed (Table 1, Entry 11). Concerning on the above outcomes, this enzyme catalysis did not arise simply from the amino acid residues on the surface of the protein.

  Table 1

  

  Table 1.  Screening of enzymes^a

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  Entry	Enzyme	Yieldb/%
  1	α-Chymotrypsin	16
  2	Lipase from porcine pancreas	None
  3	Alkaline protease	None
  4	Lipase B from Candida antarctica	None
  5	Pepsin from porcine gastric mucosa	23
  6	Trypsin from bovine pancreas	18
  7	Amano lipase M from Mucor javanicus	None
  8	Proteinase from Aspergillus melleus	None
  9	Denatured pepsinc	None
  10	Bovine serum albumin	None
  11	No enzyme	None
  a Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.2 mmol), aniline (0.22 mmol), enzyme (15 mg), and ethanol (2 mL), stirred at 50 ℃ for 36 h. b Isolated yield. c Pretreated with urea solution (8 mol/L).

  In terms of the significant role of solvents in maintaining the catalytic activity and stability of an enzyme, ^[22] various organic solvents were investigated for the pepsin-promoted reaction (Figure 1). The results showed that solvent effect had an evident impact on the reaction. The yield of 31% was obtained when methanol was applied as the solvent. Ethanol also gave the product in the yield of 22%, while low to moderate yields were obtained when other solvents were used. Additionally, no product was observed in methanol without any catalyst.

  Figure 1

  

  Figure 1.  Effect of solvent on the yield

  Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.2 mmol), aniline (0.22 mmol), pepsin (15 mg), and solvent (2 mL), stirred at 50 ℃ for 36 h. Isolated yield

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  Due to the influence of the water content in the conformational flexibility of enzyme, ^[23] the effect of water content was investigated. When the water content increased from 0 to 50% [φ(water) in methanol], a rise in the yield from 31%~41% was observed. While further increasing the water content led to a decrease in the yield. The same trend was observed in ethanol, but the effect was not as significant as that of methanol. To obtain the best yield, 50% water in methanol was selected as the optimum solvent system for the reaction.

  Temperature plays a key role in enzymatic reactions because of its effect on the reaction rate and the stability of enzymes.^[24] Thus, different reaction temperatures were examined on the pepsin-catalyzed transformation (Figure 2). When raised temperature from 30~60 ℃, the yield of product was increased to 52% after 36 h. However, when further increasing the temperature to 70 and 80 ℃, the yield decreases.

  Figure 2

  

  Figure 2.  Effect of temperature on the yield

  Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.2 mmol), aniline (0.22 mmol), enzyme (15 mg), and 50% aqueous methanol solution (2 mL), stirred at different temperatures for 36 h. Isolated yield.

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  The molar ratio of 2-(1-pyrrolidinyl)benzaldehyde and aniline in the pepsin-catalyzed reaction was then examined. When 2-(1-pyrrolidinyl)benzaldehyde and aniline were used in the molar ratio 1:3, the reaction gave a lower yield of 52%. When fixing the amount of aniline, the yield increased with increasing amounts of 2-(1-pyrro- lidinyl) benzaldehyde, and the yield of 61% was obtained when the molar ratio of 2-(1-pyrrolidinyl)benzaldehyde to aniline was 2:1. Further increasing the molar ratio of 2-(1-pyrrolidinyl)benzaldehyde and aniline could detected no significant change of yield. Thus, (2-(1-pyrrolidinyl)- benzaldehyde (0.4 mmol) to aniline (0.2 mmol) molar ratio of 2:1 was identified as the optimal ratio.

  The effect of the enzyme loading on the pepsin-cata- lyzed model reaction was investigated. The yield of the reaction is significantly affected by the enzyme loading. The reaction did not proceed without any catalyst. With the increase of the loading amount of catalyst, the yield of product increases. The yield was increased to 75% when 30 mg of enzyme was used. However, the yield of the product decreased slightly, when further increasing the amount of enzyme to 40 mg, which may be due to the fact that a larger quantity of enzyme in the system hindered the matrix diffusion. Therefore, 30 mg of pepsin was chosen as the optimum condition for the reaction of 2-(1-pyrroli- dinyl)benzaldehyde and aniline (0.50 mmol) in aqueous methanol solution.

  Having established the optimized conditions, the generality of the pepsin-catalyzed cyclocondensation reaction for the synthesis of tetrahydroquinazoline derivatives was evaluated using a variety of 2-aminobenzaldehydes (Ⅰ) to react with aromatic amines (Ⅱ) (Table 2). These results show that pepsin could tolerate different 2-aminobenzal- dehydes as acceptors and various aromatic amines as donors, including 4-methylaniline, 4-fluoroaniline, 3, 4-dime- thoxyaniline, aniline and 4-nitroaniline. When aromatic amines with electron-donating and electron-withdrawing substituents participate in this reaction (Ⅲ16, Ⅲ18, Ⅲ25, Ⅲ29), the electron-donating substituents at the para position of the benzene ring exhibit positive influence. Electronic effect on the meta position of the benzene ring has slight effect on the enzymatic method (Ⅲ3, Ⅲ13, Ⅲ17, Ⅲ23). Aromatic amines with a substituent at the ortho position can also react smoothly with 2-aminobenzalde- hyde (Ⅲ4, Ⅲ22). Methyl or methoxy substituted aromatic amines performed well in the reaction (Ⅲ16, Ⅲ18, Ⅲ22, Ⅲ29). Furthermore, halogen-substituted aromatic amines are also amenable to the reaction (Ⅲ21, Ⅲ26, Ⅲ27, Ⅲ32). Finally, 2-(azepan-1-yl)benzaldehyde and 2-(3, 4- dihydroisoquinolin-2(1H)-yl)benzaldehyde provided higher yields than those with 2-(pyrrolidin-1-yl)benzaldehyde, presumably due to the increased hydride donor capabilities of these substrates. Overall, most of the substrates tested are better reactive, and a wide range of aromatic amines can react with 2-aminobenzaldehyde to afford to corresponding products in moderate to excellent yields.

  Table 2

  

  Table 2.  Pepsin-catalyzed synthesis of tetrahydroquinazoline derivatives^a

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  a Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.4 mmol), aniline (0.2 mmol), pepsin (30 mg), and 50% aqueous methanol solution (2 mL), stirred at 60 ℃ for 36 h. Isolated yield.

  3.   Conclusions

  In summary, an efficient approach to the synthesis of tetrahydroquinazoline derivatives has been developed by using pepsin as biocatalyst through cyclocondensation reaction in aqueous methanol solution. A wide range of aromatic amines and 2-aminobenzaldehydes were investigated and their corresponding products were obtained in good yields. The effects of various parameters, such as solvent, temperature, and enzyme loading on the pepsin-catalyzed cyclocondensation reaction were investigated. Compared with existing chemical protocols, this enzymatic method is environment-friendly and easy to operate, and performs in mild conditions. Moreover, the catalyst pepsin has the advantages of being non-toxic and biodegradable.

  4.   Experimental section

  4.1   Instruments and reagents

  All major chemicals and solvents were obtained from commercial sources and used without further purification. ¹H NMR and ¹³C NMR spectra were recorded on a Bruker Avance Ⅲ-500 spectrometer (Swiss Bruker, Switzerland). Mass spectrometry were measured using a LTQ-XL linear ion trap mass spectrometer (Thermo-Fisher, USA).

  4.2   General procedure for pepsin catalyzed synthesis of tetrahydroquinazolines

  Pepsin (30 mg) was added to a solution of 2-amino- benzaldehyde (0.4 mmol) and aromatic amine (0.2 mmol) in 50% aqueous methanol solution (2 mL) and the mixture was stirred at 60 ℃ in a constant temperature incubator shaker for the specified period of time. Thin layer chromatography (TLC) was used to follow the reaction. After completion of the reaction, the organic phase was concentrated under reduced pressure to give crude product which was purified by column chromatography [V(petroleum ether):V(ethyl acetate)=10:1 or V(n-hexane):V(dich-loroethane)=1:1] to give pure product.

  4.3   Characterization data for all compounds

  4-Phenyl-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quinazo-line (Ⅲ1): Yield 75%. White solid, m.p. 82.6~84.4 ℃ (Lit.^[25] 82~84 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.32 (dd, J=10.6, 5.1 Hz, 2H), 7.20~7.10 (m, 4H), 6.96 (d, J=7.5 Hz, 1H), 6.64 (t, J=7.5 Hz, 1H), 6.54 (d, J=8.1 Hz, 1H), 4.64 (dd, J=8.3, 5.3 Hz, 1H), 4.39 (d, J=14.9 Hz, 1H), 4.13~4.11 (m, 1H), 3.46 (td, J=8.7, 3.0 Hz, 1H), 3.38 (dd, J=16.5, 8.2 Hz, 1H), 2.08 (dd, J=8.6, 3.6 Hz, 1H), 1.98 (ddd, J=9.9, 5.3, 2.3 Hz, 1H), 1.95~1.87 (m, 1H), 1.73 (ddd, J=16.5, 10.1, 5.5 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 150.3, 143.5, 129.0, 127.8, 126.0, 125.2, 124.8, 120.8, 116.2, 111.4, 76.7, 57.4, 47.1, 32.0, 22.3.

  4-(p-Tolyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quina- zoline (Ⅲ2): Yield 66%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.17~7.05 (m, 5H), 6.95 (d, J=7.5 Hz, 1H), 6.62 (t, J=7.3 Hz, 1H), 6.52 (d, J=8.0 Hz, 1H), 4.60 (dd, J=8.3, 5.2 Hz, 1H), 4.35 (d, J=14.9 Hz, 1H), 4.06 (d, J=14.9 Hz, 1H), 3.52~3.29 (m, 2H), 2.32 (s, 3H), 2.04~1.87 (m, 3H), 1.71 (ddd, J=11.5, 9.9, 5.7 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 147.7, 143.4, 134.6, 129.7, 127.8, 126.0, 125.3, 120.8, 116.1, 111.3, 76.9, 57.6, 47.1, 32.1, 22.3, 21.0; HRMS (ESI) calcd for C₁₈H₂₀N₂Na [M+Na]⁺ 287.1518, found 287.1514.

  4-(m-Tolyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quina- zoline (Ⅲ3): Yield 68%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.21 (t, J=7.5 Hz, 1H), 7.12 (t, J=7.6 Hz, 1H), 7.10~6.88 (m, 4H), 6.64 (t, J=7.4 Hz, 1H), 6.53 (d, J=8.0 Hz, 1H), 4.61 (dd, J=8.3, 5.2 Hz, 1H), 4.34 (d, J=14.8 Hz, 1H), 4.10 (d, J=14.8 Hz, 1H), 3.53~3.33 (m, 2H), 2.34 (s, 3H), 2.11~1.84 (m, 3H), 1.73 (tt, J=11.5, 8.2 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 150.3, 143.3, 138.7, 128.8, 127.8, 125.9, 125.9, 125.6, 121.9, 120.8, 116.1, 111.3, 76.7, 57.5, 47.1, 32.1, 22.3, 21.5; HRMS (ESI) calcd for C₁₈H₂₀N₂Na [M+Na]⁺ 287.1518, found 287.1514.

  4-(o-Tolyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quina- zoline (Ⅲ4): Yield 55%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.27~7.19 (m, 1H), 7.15 (t, J=7.9 Hz, 2H), 7.08 (t, J=7.1 Hz, 2H), 6.94 (d, J=7.3 Hz, 1H), 6.64 (t, J=7.3 Hz, 1H), 6.57 (d, J=8.0 Hz, 1H), 4.74 (t, J=14.4 Hz, 1H), 4.14 (s, 1H), 3.89 (d, J=15.0 Hz, 1H), 3.52 (t, J=7.2 Hz, 1H), 3.37 (dd, J=16.2, 8.6 Hz, 1H), 2.33 (d, J=12.1 Hz, 3H), 2.05~1.81 (m, 3H), 1.51 (tt, J=11.6, 8.1 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 146.1, 143.8, 136.7, 130.6, 127.6, 126.7, 126.0, 125.1, 115.9, 111.8, 109.7, 99.9, 76.4, 56.7, 47.7, 32.7, 22.5, 18.0; HRMS (ESI) calcd for C₁₈H₂₀N₂Na [M+Na]⁺ 287.1518, found 287.1514.

  4-(4-Methoxyphenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo- [1, 2-a]quinazoline (Ⅲ5): Yield 50%. White solid, m.p. 73.7~75.3 ℃ (Lit.^[25] 73~75 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.16~7.08 (m, 3H), 6.95 (d, J=7.2 Hz, 1H), 6.88~6.82 (m, 2H), 6.63 (t, J=7.1 Hz, 1H), 6.52 (d, J=8.0 Hz, 1H), 4.56 (dd, J=8.3, 5.5 Hz, 1H), 4.36 (d, J=14.9 Hz, 1H), 4.01 (d, J=14.9 Hz, 1H), 3.79 (s, 3H), 3.46 (td, J=8.6, 2.6 Hz, 1H), 3.36 (dd, J=15.9, 8.6 Hz, 1H), 2.01~1.82 (m, 3H), 1.69 (ddd, J=11.2, 8.3, 3.6 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 157.1, 143.4, 143.1, 127.8, 126.80, 126.1, 120.8, 116.0, 114.2, 111.2, 77.3, 57.6, 55.4, 47.1, 32.0, 22.3.

  4-(4-Fluorophenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quinazoline (Ⅲ6): Yield 60%. White solid, m.p. 98.1~98.6 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.20~7.07 (m, 3H), 7.05~6.90 (m, 3H), 6.65 (t, J=7.3 Hz, 1H), 6.53 (d, J=8.0 Hz, 1H), 4.59 (dd, J=7.9, 5.1 Hz, 1H), 4.37 (d, J=14.9 Hz, 1H), 4.03 (d, J=14.9 Hz, 1H), 3.55~3.27 (m, 2H), 2.03~1.83 (m, 3H), 1.70~1.62 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 146.08, 143.38, 127.90, 127.19, 126.0, 120.5, 116.2, 115.8, 115.6, 111.3, 77.0, 57.5, 47.1, 31.8, 22.3; HRMS (ESI) calcd for C₁₇H₁₇FN₂Na [M+ Na]⁺ 291.1268, found 291.1264.

  4-(4-Chlorophenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quinazoline (Ⅲ7): Yield 61%. White solid, m.p. 99.0~99.5 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.25 (dd, J=9.5, 2.7 Hz, 2H), 7.13 (t, J=7.5 Hz, 1H), 7.11~7.03 (m, 2H), 6.95 (d, J=7.5 Hz, 1H), 6.65 (t, J=7.3 Hz, 1H), 6.53 (d, J=8.0 Hz, 1H), 4.60 (dd, J=8.3, 5.3 Hz, 1H), 4.37 (d, J=15.0 Hz, 1H), 4.08 (d, J=5.0 Hz, 1H), 3.49~3.28 (m, 2H), 2.13~1.81 (m, 3H), 1.68 (tt, J=11.2, 8.3 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.7, 143.4, 130.1, 129.1, 128.0, 126.6, 126.0, 120.5, 116.4, 111.4, 76.6, 57.2, 47.0, 31.8, 22.2; HRMS (ESI) calcd for C₁₇H₁₇ClN₂Na [M+ Na]⁺ 307.0972, found 307.0973.

  4-(4-Bromophenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quinazoline (Ⅲ8): Yield 52%. White solid, m.p. 97.6~99.1 ℃ (Lit.^[25] 97~99 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.41 (d, J=8.6 Hz, 2H), 7.14 (t, J=7.6 Hz, 1H), 7.04 (d, J=8.5 Hz, 2H), 6.96 (d, J=7.3 Hz, 1H), 6.66 (t, J=7.3 Hz, 1H), 6.52 (d, J=7.0 Hz, 1H), 4.61 (dd, J=8.2, 5.4 Hz, 1H), 4.37 (d, J=15.0 Hz, 1H), 4.08 (d, J=15.0 Hz, 1H), 3.54~3.38 (m, 1H), 3.38~3.29 (m, 1H), 2.11~1.88 (m, 3H), 1.69 (ddd, J=20.0, 11.3, 8.4 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.0, 143.4, 132.0, 128.0, 126.9, 126.0, 120.3, 117.9, 116.4, 111.5, 76.6, 57.1, 47.0, 31.7, 22.2.

  4-(4-Iodophenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]-quinazoline (Ⅲ9): Yield 43%. White solid, m.p. 73.7~74.0 ℃ (Lit.^[26] 72~74 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.60 (d, J=8.6 Hz, 2H), 7.14 (t, J=7.6 Hz, 1H), 6.92 (dd, J=28.0, 7.0 Hz, 3H), 6.66 (t, J=7.3 Hz, 1H), 6.53 (d, J=8.0 Hz, 1H), 4.61 (dd, J=8.3, 5.3 Hz, 1H), 4.37 (d, J=15.0 Hz, 1H), 4.08 (d, J=14.0 Hz, 1H), 3.49~3.28 (m, 2H), 2.14~2.03 (m, 1H), 2.02~1.84 (m, 2H), 1.70 (tt, J=11.1, 8.4 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.9, 143.5, 138.0, 128.0, 127.1, 125.9, 120.5, 116.4, 111.4, 88.6, 76.4, 57.0, 47.0, 31.7, 22.2.

  4-(1, 2, 3, 3a-Tetrahydropyrrolo[1, 2-a]quinazolin-4(5H)- yl)benzonitrile (Ⅲ10): Yield 49%. White solid, m.p. 116.3~117.2 ℃ (Lit.^[25] 116~118 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.53 (d, J=8.8 Hz, 2H), 7.20 (t, J=7.4 Hz, 1H), 7.03 (dd, J=17.1, 8.2 Hz, 3H), 6.77 (t, J=7.4 Hz, 1H), 6.64 (d, J=8.0 Hz, 1H), 4.58 (dd, J=8.3, 5.5 Hz, 1H), 4.46 (d, J=14.7 Hz, 1H), 4.29 (d, J=14.7 Hz, 1H), 3.44 (td, J=8.3, 6.4 Hz, 1H), 3.33 (td, J=8.8, 5.3 Hz, 1H), 2.37 (tdd, J=8.4, 5.5, 3.3 Hz, 1H), 2.14~1.92 (m, 2H), 1.77 (ddd, J=18.0, 12.2, 9.1 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 152.9, 144.3, 133.1, 128.3, 125.7, 122.2, 120.1, 119.7, 118.1, 112.2, 103.3, 75.0, 52.6, 46.2, 31.3, 21.5.

  4-(4-Nitrophenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]-quinazoline (Ⅲ11): Yield 43%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 8.18~8.11 (m, 2H), 7.24 (t, J=7.5 Hz, 1H), 7.10 (d, J=7.3 Hz, 1H), 6.93~6.86 (m, 2H), 6.83 (t, J=7.3 Hz, 1H), 6.71 (d, J=7.9 Hz, 1H), 4.59~4.49 (m, 2H), 4.36 (d, J=14.3 Hz, 1H), 3.51 (td, J=8.7, 4.8 Hz, 1H), 3.29 (td, J=8.9, 6.6 Hz, 1H), 2.59~2.46 (m, 1H), 2.17~1.95 (m, 2H), 1.82 (ddt, J=12.3, 10.0, 8.2 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 153.7, 144.6, 139.4, 128.4, 125.6, 125.5, 123.4, 119.0, 116.2, 112.6, 74.5, 50.5, 45.6, 31.2, 21.1; HRMS (ESI) calcd for C₁₇H₁₇N₃O₂Na [M+Na]⁺ 318.1213, found 318.1210.

  4-(3, 4-Dimethoxyphenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrro- lo[1, 2-a]quinazoline (Ⅲ12): Yield 41%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.13 (t, J=7.5 Hz, 1H), 6.95 (d, J=7.1 Hz, 1H), 6.87~6.69 (m, 3H), 6.64 (t, J=7.3 Hz, 1H), 6.52 (d, J=8.0 Hz, 1H), 4.59 (dd, J=7.9, 5.1 Hz, 1H), 4.37 (d, J=14.8 Hz, 1H), 4.04 (d, J=14.8 Hz, 1H), 3.85 (d, J=22.8 Hz, 6H), 3.57~3.29 (m, 2H), 2.12~1.81 (m, 3H), 1.71 (dt, J=19.4, 8.4 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.9, 146.7, 143.2, 127.8, 126.1, 120.6, 116.7, 116.0, 111.2, 111.1, 110.2, 57.7, 56.0, 55.8, 47.2, 32.0, 22.3; HRMS (ESI) calcd for C₁₉H₂₂N₂O₂Na [M+Na]⁺ 333.1573, found 333.1566.

  4-(3-Chlorophenyl)-1, 2, 3, 3a, 4, 5-hexahydropyrrolo[1, 2-a]quinazoline (Ⅲ13): Yield 74%. White solid, m.p. 70.9~71.5 ℃ (Lit.^[26] 70~71 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.22 (dd, J=14.3, 6.3 Hz, 1H), 7.18~7.11 (m, 2H), 7.09 (d, J=7.9 Hz, 1H), 7.03 (d, J=7.0 Hz, 1H), 6.96 (d, J=7.3 Hz, 1H), 6.67 (t, J=7.4 Hz, 1H), 6.54 (d, J=8.0 Hz, 1H), 4.60 (dd, J=8.3, 5.3 Hz, 1H), 4.35 (d, J=14.9 Hz, 1H), 4.12 (d, J=14.9 Hz, 1H), 3.52~3.30 (m, 2H), 2.11 (ddd, J=12.2, 7.3, 2.3 Hz, 1H), 2.05~1.86 (m, 2H), 1.72 (tt, J=11.2, 8.3 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 151.5, 143.4, 134.3, 129.9, 127.9, 125.9, 124.7, 124.5, 123.1, 120.5, 116.4, 111.5, 76.3, 56.9, 47.0, 31.8, 22.2.

  4-(4-(Trifluoromethyl)phenyl)-1, 2, 3, 3a, 4, 5-hexahydrop-yrrolo[1, 2-a]quinazoline (Ⅲ14): Yield 76%. White solid, m.p. 73.4~73.9 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.53 (d, J=8.5 Hz, 2H), 7.15 (d, J=8.3 Hz, 3H), 6.99 (d, J=7.3 Hz, 1H), 6.70 (t, J=7.4 Hz, 1H), 6.57 (d, J=8.0 Hz, 1H), 4.65 (dd, J=8.3, 5.4 Hz, 1H), 4.42 (d, J=15.0 Hz, 1H), 4.21 (d, J=15.0 Hz, 1H), 3.48~3.32 (m, 2H), 2.22 (tdd, J=7.7, 5.5, 2.7 Hz, 1H), 2.08~1.87 (m, 2H), 1.74 (ddd, J=18.9, 12.0, 8.6 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 153.0, 143.8, 128.1, 126.1, 126.1, 125.9, 123.2, 120.9, 117.0, 111.7, 75.9, 55.7, 46.8, 31.6, 22.0; HRMS (ESI) calcd for C₁₈H₁₇F₃N₂Na [M+Na]⁺ 341.1236, found 341.1236.

  6-Phenyl-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino[1, 2-a]qui-nazoline (Ⅲ15): Yield 84%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.24~7.20 (m, 2H), 7.09 (t, J=7.4 Hz, 1H), 7.01 (d, J=7.5 Hz, 1H), 6.95 (d, J=7.9 Hz, 2H), 6.83 (t, J=7.3 Hz, 1H), 6.64~6.55 (m, 2H), 4.88 (dd, J=9.9, 4.2 Hz, 1H), 4.58 (d, J=16.1 Hz, 1H), 4.38 (d, J=16.1 Hz, 1H), 3.88 (ddd, J=15.0, 6.3, 3.2 Hz, 1H), 3.28~3.18 (m, 1H), 2.18~2.09 (m, 1H), 1.97~1.84 (m, 2H), 1.68~1.58 (m, 3H), 1.48 (ddd, J=17.2, 9.6, 4.0 Hz, 1H), 1.35 (ddd, J=13.6, 8.8, 4.5 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.8, 142.6, 129.3, 129.2, 127.8, 126.5, 117.8, 117.4, 115.6, 110.1, 75.1, 47.1, 46.3, 33.0, 26.4, 26.0, 24.8; HRMS (ESI) calcd for C₁₉H₂₂N₂Na [M+Na]⁺ 301.1675, found 301.1672.

  6-(p-Tolyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino[1, 2-a]-quinazoline (Ⅲ16): Yield 92%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.11~6.95 (m, 4H), 6.86 (d, J=8.5 Hz, 2H), 6.64~6.53 (m, 2H), 4.80 (dd, J=10.1, 4.0 Hz, 1H), 4.56 (d, J=16.2 Hz, 1H), 4.31 (d, J=16.2 Hz, 1H), 3.85 (ddd, J=15.0, 6.3, 3.3 Hz, 1H), 3.27~3.13 (m, 1H), 2.24 (s, 3H), 2.13 (dtd, J=16.2, 10.8, 5.4 Hz, 1H), 1.96~1.78 (m, 2H), 1.72~1.56 (m, 3H), 1.54~1.41 (m, 1H), 1.40~1.28 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 147.7, 142.7, 129.7, 129.5, 127.7, 126.6, 117.9, 117.9, 115.5, 110.0, 75.7, 47.1, 46.5, 33.1, 26.4, 26.1, 24.8, 20.6; HRMS (ESI) calcd for C₂₀H₂₄N₂Na [M+Na]⁺ 315.1831, found 315.1827.

  6-(m-Tolyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino[1, 2-a]-quinazoline (Ⅲ17): Yield 89%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.14~7.04 (m, 2H), 7.00 (d, J=7.2 Hz, 1H), 6.75 (d, J=8.5 Hz, 2H), 6.68~6.54 (m, 3H), 4.87 (dd, J=9.9, 4.2 Hz, 1H), 4.56 (d, J=16.1 Hz, 1H), 4.37 (d, J=16.1 Hz, 1H), 3.88 (ddd, J=15.0, 6.3, 3.1 Hz, 1H), 3.29~3.19 (m, 1H), 2.30 (s, 3H), 2.19~2.10 (m, 1H), 1.94~1.81 (m, 2H), 1.70~1.58 (m, 3H), 1.53~1.44 (m, 1H), 1.35 (ddd, J=18.6, 9.2, 4.2 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.7, 142.6, 138.8, 129.9, 127.7, 126.5, 120.8, 118.1, 117.9, 115.6, 114.3, 110.1, 75.1, 47.1, 46.3, 32.7, 26.4, 26.0, 24.8, 21.9; HRMS (ESI) calcd for C₂₀H₂₄N₂Na [M+Na]⁺ 315.1831, found 315.1886.

  6-(4-Methoxyphenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroaze- pino[1, 2-a]quinazoline (Ⅲ18): Yield 95%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.07 (t, J=7.5 Hz, 1H), 6.94 (dd, J=24.2, 8.1 Hz, 3H), 6.82~6.71 (m, 2H), 6.65~6.52 (m, 2H), 4.72~4.53 (m, 2H), 4.23 (d, J=16.3 Hz, 1H), 3.88~3.76 (m, 1H), 3.72 (s, 3H), 3.16 (ddd, J=15.4, 10.2, 5.6 Hz, 1H), 2.16~2.05 (m, 1H), 1.95 (d, J=6.1 Hz, 1H), 1.86 (dtd, J=13.5, 10.1, 3.6 Hz, 1H), 1.74~1.54 (m, 3H), 1.53~1.41 (m, 1H), 1.34 (dtd, J=14.1, 9.8, 4.4 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 154.1, 144.4, 142.81, 127.7, 126.5, 120.3, 117.8, 115.4, 114.4, 109.9, 76.8, 55.5, 47.3, 47.0, 33.9, 26.4, 26.2, 24.8; HRMS (ESI) calcd for C₂₀H₂₄N₂ONa [M+Na]⁺ 331.1780, found 331.1774.

  6-(4-(Trifluoromethyl)phenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahy-droazepino[1, 2-a]quinazoline (Ⅲ19): Yield 82%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.47 (d, J=8.7 Hz, 2H), 7.10 (t, J=7.8 Hz, 1H), 7.02 (d, J=7.4 Hz, 1H), 6.94 (d, J=8.7 Hz, 2H), 6.69~6.60 (m, 2H), 4.96 (dd, J=9.3, 5.0 Hz, 1H), 4.51 (dd, J=45.7, 16.0 Hz, 2H), 3.91 (ddd, J=15.1, 6.6, 3.0 Hz, 1H), 3.3~3.19 (m, 1H), 2.17 (ddt, J=20.3, 10.4, 6.2 Hz, 1H), 1.91~1.83 (m, 2H), 1.71~1.62 (m, 3H), 1.54~1.47 (m, 1H), 1.39~1.33 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 151.5, 142.4, 128.0, 126.7, 126.6, 126.5, 125.8, 117.5, 116.1, 115.3, 110.5, 73.8, 47.3, 45.9, 32.4, 26.6, 25.8, 24.7; HRMS (ESI) calcd for C₂₀H₂₁F₃N₂Na [M+H]⁺ 347.1729, found 347.1726.

  4-(6a, 7, 8, 9, 10, 11-Hexahydroazepino[1, 2-a]quinazolin- 6(5H)-yl)benzonitrile (Ⅲ20): Yield 83%. White solid, m.p. 142.7~143.2 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.50 (d, J=8.9 Hz, 2H), 7.12 (t, J=7.4 Hz, 1H), 7.03 (d, J=7.3 Hz, 1H), 6.87 (d, J=8.9 Hz, 2H), 6.73~6.61 (m, 2H), 5.07~4.93 (m, 1H), 4.57~4.42 (m, 2H), 3.92 (ddd, J=15.1, 6.6, 2.7 Hz, 1H), 3.35~3.21 (m, 1H), 2.25~2.12 (m, 1H), 1.86 (dd, J=12.7, 6.9 Hz, 2H), 1.76~1.56 (m, 3H), 1.56~1.45 (m, 1H), 1.45~1.33 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 151.3, 142.2, 133.6, 128.2, 126.6, 120.1, 117.4, 116.6, 114.6, 110.9, 100.2, 72.8, 47.5, 45.5, 31.8, 26.9, 25.6, 24.6; HRMS (ESI) calcd for C₂₀H₂₁N₃Na [M+Na]⁺ 326.1627, found 326.1620.

  6-(4-Chlorophenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino-[1, 2-a]quinazoline (Ⅲ21): Yield 85%. White solid, m.p. 95.1~95.6 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.22~7.14 (m, 2H), 7.09 (t, J=7.5 Hz, 1H), 6.98 (d, J=7.2 Hz, 1H), 6.90~6.83 (m, 2H), 6.66~6.56 (m, 2H), 4.79 (dd, J=10.0, 4.2 Hz, 1H), 4.56 (d, J=16.2 Hz, 1H), 4.31 (d, J=16.2 Hz, 1H), 3.87 (ddd, J=15.0, 6.3, 3.3 Hz, 1H), 3.25~3.14 (m, 1H), 2.20~2.09 (m, 1H), 1.96~1.81 (m, 2H), 1.67 (dddd, J=27.8, 13.9, 8.7, 4.8 Hz, 3H), 1.54~1.43 (m, 1H), 1.40~1.30 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.5, 1 42.5, 129.0, 127.9, 126.5, 124.8, 118.8, 117.4, 115.8, 110.2, 75.3, 47.1, 46.5, 33.2, 26.4, 26.0, 24.7; HRMS (ESI) calcd for C₁₉H₂₁ClN₂Na [M+Na]⁺ 335.1285, found 335.1278.

  6-(o-Tolyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino[1, 2-a]-quinazoline (Ⅲ22): Yield 90%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.07 (d, J=7.24 Hz, 1H), 7.03 (t, J=7.7 Hz, 1H), 6.93 (dd, J=10.8, 4.3 Hz, 1H), 6.85 (dd, J=13.6, 6.9 Hz, 3H), 6.52 (t, J=7.1 Hz, 2H), 4.65 (d, J=16.9 Hz, 1H), 4.16 (dd, J=10.1, 4.3 Hz, 1H), 3.88 (d, J=16.9 Hz, 1H), 3.09~2.86 (m, 1H), 2.26 (s, 3H), 2.11~1.85 (m, 3H), 1.64~1.24 (m, 6H); ¹³C NMR (126 MHz, CDCl₃) δ: 151.3, 143.3, 132.8, 130.9, 127.7, 126.7, 126.2, 123.4, 121.8, 118.4, 115.3, 109.6, 77.0, 47.8, 46.9, 35.4, 26.5, 26.2, 24.9, 18.5; HRMS (ESI) calcd for C₂₀H₂₄N₂Na [M+Na]⁺ 315.1831, found 315.1827.

  6-(3-Chlorophenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino-[1, 2-a]quinazoline (Ⅲ23): Yield 82%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.15~7.07 (m, 2H), 7.00 (d, J=7.4 Hz, 1H), 6.89 (t, J=2.1 Hz, 1H), 6.82~6.77 (m, 2H), 6.67~6.59 (m, 2H), 4.88~4.80 (m, 1H), 4.54 (d, J=16.0 Hz, 1H), 4.37 (d, J=16.1 Hz, 1H), 3.90 (ddd, J=15.1, 6.5, 3.0 Hz, 1H), 3.25 (ddd, J=15.8, 10.3, 5.9 Hz, 1H), 2.15 (ddt, J=12.2, 10.5, 6.1 Hz, 1H), 1.91~1.82 (m, 2H), 1.71~1.60 (m, 3H), 1.53~1.45 (m, 1H), 1.40~1.31 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 150.7, 142.5, 135.0, 130.2, 128.0, 126.6, 119.5, 117.5, 116.7, 116.0, 114.9, 110.4, 74.5, 47.2, 46.2, 32.7, 26.5, 26.0, 24.7; HRMS (ESI) calcd for C₁₉H₂₂ClN₂ [M+H]⁺ 313.1466, found 313.1462.

  6-(4-Nitrophenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino-[1, 2-a]quinazoline (Ⅲ24): Yield 71%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 8.14 (d, J=9.3 Hz, 2H), 7.15 (t, J=7.5 Hz, 1H), 7.05 (d, J=7.3 Hz, 1H), 6.82 (d, J=9.3 Hz, 2H), 6.78~6.64 (m, 2H), 5.09 (t, J=7.3 Hz, 1H), 4.54 (q, J=15.9 Hz, 2H), 3.93 (ddd, J=15.3, 6.4, 2.4 Hz, 1H), 3.38~3.23 (m, 1H), 2.25~2.13 (m, 1H), 1.87 (dd, J=12.9, 6.9 Hz, 2H), 1.78~1.66 (m, 2H), 1.66~1.48 (m, 2H), 1.47~1.35 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 152.5, 142.2, 138.3, 128.3, 126.6, 126.1, 117.5, 116.9, 112.6, 111.2, 72.4, 47.7, 45.6, 31.4, 27.1, 25.5, 24.6; HRMS (ESI) calcd for C₁₉H₂₁N₃O₂Na [M+H]⁺ 324.1706, found 324.1702.

  6-(3, 4-Dimethoxyphenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroa-zepino[1, 2-a]quinazoline (Ⅲ25): Yield 89%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.09 (t, J=7.5 Hz, 1H), 6.98 (d, J=7.5 Hz, 1H), 6.72 (d, J=8.7 Hz, 1H), 6.60 (dd, J=17.2, 8.6 Hz, 3H), 6.49 (dd, J=8.6, 2.3 Hz, 1H), 4.74~4.55 (m, 2H), 4.24 (d, J=16.0 Hz, 1H), 3.83 (t, J=13.5 Hz, 7H), 3.19 (ddd, J=15.4, 10.1, 5.6 Hz, 1H), 2.12 (qd, J=10.7, 5.5 Hz, 1H), 2.03~1.82 (m, 2H), 1.77~1.56 (m, 3H), 1.54~1.44 (m, 1H), 1.41~1.31 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.3, 144.9, 143.8, 142.7, 127.8, 126.4, 117.8, 115.5, 111.8, 110.4, 109.9, 104.6, 76.9, 56.2, 55.9, 47.5, 47.0, 33.9, 26.3, 26.2, 24.8; HRMS (ESI) calcd for C₂₁H₂₆N₂O₂Na [M+Na]⁺ 361.1886, found 361.1877.

  6-(4-Bromophenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino-[1, 2-a]quinazoline (Ⅲ26): Yield 88%. White solid, m.p. 105.3~107.6 ℃ (Lit.^[25] 105~108 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.34~7.28 (m, 2H), 7.10 (t, J=7.4 Hz, 1H), 6.98 (d, J=7.5 Hz, 1H), 6.85~6.78 (m, 2H), 6.67~6.55 (m, 2H), 4.80 (dd, J=10.0, 4.2 Hz, 1H), 4.55 (d, J=16.2 Hz, 1H), 4.32 (d, J=16.2 Hz, 1H), 3.87 (ddd, J=15.0, 6.4, 3.2 Hz, 1H), 3.22 (ddd, J=15.6, 10.2, 5.8 Hz, 1H), 2.24~2.08 (m, 1H), 1.96~1.80 (m, 2H), 1.74~1.60 (m, 3H), 1.54~1.44 (m, 1H), 1.41~1.30 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.9, 142.5, 132.0, 128.0, 126.6, 119.1, 117.4, 115.9, 112.1, 110.2, 75.0, 47.2, 46.4, 33.1, 26.4, 26.0, 24.8.

  6-(4-Iodophenyl)-5, 6, 6a, 7, 8, 9, 10, 11-octahydroazepino-[1, 2-a]quinazoline (Ⅲ27): Yield 93%. Viscous liquid. ¹H NMR (500 MHz, CDCl₃) δ: 7.48 (d, J=8.6 Hz, 2H), 7.09 (t, J=7.7 Hz, 1H), 6.99 (d, J=7.3 Hz, 1H), 6.77~6.53 (m, 4H), 4.81 (dd, J=9.9, 4.1 Hz, 1H), 4.53 (d, J=16.1 Hz, 1H), 4.32 (d, J=16.1 Hz, 1H), 3.87 (ddd, J=14.8, 6.2, 3.0 Hz, 1H), 3.34~3.05 (m, 1H), 2.23~2.08 (m, 1H), 1.96~1.78 (m, 2H), 1.77~1.58 (m, 3H), 1.48 (ddd, J=18.4, 11.9, 3.8 Hz, 1H), 1.41~1.29 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.4, 142.4, 137.9, 127.9, 126.6, 119.4, 117.4, 115.8, 110.2, 81.8, 74.8, 47.2, 46.2, 32.9, 26.4, 26.0, 24.7; HRMS (ESI) calcd for C₁₉H₂₁IN₂Na [M+Na]⁺ 427.0641, found 427.0639.

  5-Phenyl-4b, 5, 12, 13-tetrahydro-6H-isoquinolino[2, 1-a]-quinazoline (Ⅲ28): Yield 88%. White solid, m.p. 139.4~141.9 ℃ (Lit.^[25] 139~141 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 7.60 (d, J=7.4 Hz, 1H), 7.32~7.11 (m, 6H), 7.08 (t, J=7.5 Hz, 1H), 7.02 (d, J=7.2 Hz, 1H), 6.95 (d, J=8.2 Hz, 1H), 6.88 (t, J=6.6 Hz, 2H), 6.66 (t, J=7.3 Hz, 1H), 6.03 (s, 1H), 4.40 (d, J=16.6 Hz, 1H), 4.32 (d, J=16.6 Hz, 1H), 4.22 (dd, J=14.4, 5.2 Hz, 1H), 3.45 (td, J=14.2, 3.8 Hz, 1H), 3.22~3.02 (m, 1H), 2.62~2.42 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 150.9, 143.8, 137.4, 136.7, 129.3, 129.0, 127.7, 127.6, 127.0, 126.4, 126.0, 122.2, 120.8, 118.5, 118.1, 113.7, 73.9, 46.5, 45.3, 25.0.

  5-(p-Tolyl)-4b, 5, 12, 13-tetrahydro-6H-isoquinolino[2, 1-a]quinazoline (Ⅲ29): Yield 93%. White solid, m.p. 159.5~160.0 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.71 (d, J=7.5 Hz, 1H), 7.34~7.23 (m, 2H), 7.20~7.06 (m, 6H), 7.02 (d, J=8.1 Hz, 1H), 6.96 (d, J=7.0 Hz, 1H), 6.73 (t, J=7.1 Hz, 1H), 6.05 (s, 1H), 4.47 (d, J=16.7 Hz, 1H), 4.31 (dd, J=26.7, 11.2 Hz, 2H), 3.51 (t, J=11.9 Hz, 1H), 3.19 (t, J=11.8 Hz, 1H), 2.59 (d, J=16.3 Hz, 1H), 2.32 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.6, 143.9, 137.5, 136.7, 130.4, 129.8, 128.9, 127.6, 127.5, 126.9, 126.4, 126.0, 122.2, 119.0, 118.0, 113.6, 74.5, 46.7, 45.3, 25.0, 20.7; HRMS (ESI) calcd for C₂₃H₂₂N₂Na [M+Na]⁺ 349.1675, found 349.1668.

  5-(m-Tolyl)-4b, 5, 12, 13-tetrahydro-6H-isoquinolino[2, 1-a]quinazoline (Ⅲ30): Yield 86%. White solid, m.p. 121.6~122.1 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.57 (d, J=7.5 Hz, 1H), 7.23~7.05 (m, 4H), 7.02 (d, J=7.3 Hz, 1H), 6.99~6.91 (m, 3H), 6.88 (d, J=7.3 Hz, 1H), 6.77~6.58 (m, 2H), 6.04 (s, 1H), 4.39 (d, J=16.6 Hz, 1H), 4.30 (d, J=16.7 Hz, 1H), 4.23 (dd, J=14.5, 5.3 Hz, 1H), 3.54~3.38 (m, 1H), 3.20~3.03 (m, 1H), 2.51 (dd, J=16.6, 3.4 Hz, 1H), 2.29 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 150.9, 143.8, 139.0, 137.5, 136.7, 129.2, 129.0, 127.7, 127.6, 126.9, 126.4, 126.0, 122.2, 121.6, 119.1, 118.1, 115.3, 113.7, 73.9, 46.3, 45.4, 24.9, 21.9; HRMS (ESI) calcd for C₂₃H₂₂N₂Na [M+Na]⁺ 349.1675, found 349.1668.

  5-(4-Fluorophenyl)-4b, 5, 12, 13-tetrahydro-6H-isoquino- lino[2, 1-a]quinazoline (Ⅲ31): Yield 81%. White solid, m.p. 142.2~142.7 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.65 (d, J=7.6 Hz, 1H), 7.27~7.14 (m, 2H), 7.14~7.05 (m, 3H), 7.03 (d, J=7.4 Hz, 1H), 6.99~6.82 (m, 4H), 6.67 (t, J=7.3 Hz, 1H), 5.87 (s, 1H), 4.40 (d, J=16.8 Hz, 1H), 4.27~4.15 (m, 2H), 3.52~3.31 (m, 1H), 3.19~2.97 (m, 1H), 2.52 (dd, J=16.5, 3.2 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 158.8, 156.9, 147.3, 143.9, 137.1, 136.6, 129.0, 127.8, 127.0, 126.4, 126.1, 121.9, 121.2, 121.1, 118.2, 115.7, 115.6, 113.7, 74.8, 47.7, 45.1, 25.2; HRMS (ESI) calcd for C₂₂H₁₉FN₂Na [M+Na]⁺ 353.1424, found 353.1422.

  5-(4-Chlorophenyl)-4b, 5, 12, 13-tetrahydro-6H-isoquinolino[2, 1-a]quinazoline (Ⅲ32): Yield 67%. White solid, m.p. 126.8~127.3 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.56 (d, J=7.4 Hz, 1H), 7.26~7.13 (m, 4H), 7.14~7.01 (m, 4H), 6.96 (d, J=8.3 Hz, 1H), 6.88 (d, J=7.3 Hz, 1H), 6.68 (t, J=7.3 Hz, 1H), 5.96 (s, 1H), 4.40 (d, J=16.6 Hz, 1H), 4.25 (dt, J=20.5, 7.4 Hz, 2H), 3.51~3.35 (m, 1H), 3.17~3.02 (m, 1H), 2.54 (dd, J=16.6, 3.5 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.4, 143.7, 136.9, 136.6, 129.1, 129.04, 127.84, 127.68, 126.97, 126.42, 125.88, 125.71, 121.7, 120.1, 118.3, 113.8, 74.0, 47.0, 45.3, 25.0; HRMS (ESI) calcd for C₂₂H₂₀ClN₂ [M+H]⁺ 347.1309, found 347.1304.

  5-(4-(Trifluoromethyl)phenyl)-4b, 5, 12, 13-tetrahydro- 6H-isoquinolino[2, 1-a]quinazoline (Ⅲ33): Yield 71%. White solid, m.p. 139.8~141.7 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.54~7.39 (m, 3H), 7.25~7.08 (m, 5H), 7.07~7.01 (m, 1H), 6.98 (d, J=8.2 Hz, 1H), 6.90 (d, J=7.3 Hz, 1H), 6.69 (t, J=7.3 Hz, 1H), 6.12 (s, 1H), 4.50~4.33 (m, 2H), 4.26 (dd, J=14.5, 5.3 Hz, 1H), 3.50 (td, J=14.3, 4.0 Hz, 1H), 3.22~3.03 (m, 1H), 2.56 (dd, J=16.7, 3.3 Hz, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 153.0, 143.5, 136.5, 136.5, 129.2, 128.0, 127.8, 127.0, 126.7, 126.6, 126.5, 125.7, 121.6, 118.6, 116.9, 114.0, 72.8, 46.3, 45.5, 24.8; HRMS (ESI) calcd for C₂₃H₁₉F₃N₂Na [M+Na]⁺ 403.1392, found 403.1378.

  4-(12, 13-Dihydro-6H-isoquinolino[2, 1-a]quinazolin-5- (4bH)-yl)benzonitrile (Ⅲ34): Yield 43%. White solid, m.p. 174.6~175.1 ℃; ¹H NMR (500 MHz, CDCl₃) δ: 7.53 (d, J=8.5 Hz, 2H), 7.31 (d, J=6.4 Hz, 1H), 7.12 (ddd, J=36.9, 18.5, 9.3 Hz, 6H), 7.01 (d, J=8.2 Hz, 1H), 6.92 (d, J=7.3 Hz, 1H), 6.72 (t, J=7.3 Hz, 1H), 6.17 (s, 1H), 4.52~4.36 (m, 2H), 4.29 (dd, J=14.4, 5.3 Hz, 1H), 3.61~3.46 (m, 1H), 3.23~3.07 (m, 1H), 2.67~2.51 (m, 1H); ¹³C NMR (126 MHz, CDCl₃) δ: 153.3, 143.2, 136.4, 135.9, 133.7, 129.3, 128.1, 128.0, 127.0, 126.5, 125.4, 121.2, 119.9, 118.8, 116.3, 114.2, 101.7, 72.0, 45.9, 45.6, 24.6; HRMS (ESI) calcd for C₂₃H₁₉N₃Na [M+Na]⁺ 360.1471, found 360.1465.

  Supporting Information  ¹H NMR and ¹³C NMR spectra for all compounds, HRMS spectra for novel compounds. The Supporting Information is available free of charge via the Internet at http://sioc-journal.cn/.

  
  
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• 

  Scheme 1  Pepsin-catalyzed cyclocondensation of 2-aminoben- zaldehyde and aromatic amine

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  Figure 1  Effect of solvent on the yield

  Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.2 mmol), aniline (0.22 mmol), pepsin (15 mg), and solvent (2 mL), stirred at 50 ℃ for 36 h. Isolated yield

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  Figure 2  Effect of temperature on the yield

  Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.2 mmol), aniline (0.22 mmol), enzyme (15 mg), and 50% aqueous methanol solution (2 mL), stirred at different temperatures for 36 h. Isolated yield.

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  Table 1.  Screening of enzymes^a

  Entry	Enzyme	Yieldb/%
  1	α-Chymotrypsin	16
  2	Lipase from porcine pancreas	None
  3	Alkaline protease	None
  4	Lipase B from Candida antarctica	None
  5	Pepsin from porcine gastric mucosa	23
  6	Trypsin from bovine pancreas	18
  7	Amano lipase M from Mucor javanicus	None
  8	Proteinase from Aspergillus melleus	None
  9	Denatured pepsinc	None
  10	Bovine serum albumin	None
  11	No enzyme	None
  a Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.2 mmol), aniline (0.22 mmol), enzyme (15 mg), and ethanol (2 mL), stirred at 50 ℃ for 36 h. b Isolated yield. c Pretreated with urea solution (8 mol/L).

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  Table 2.  Pepsin-catalyzed synthesis of tetrahydroquinazoline derivatives^a

  a Reaction conditions: 2-(1-pyrrolidinyl)benzaldehyde (0.4 mmol), aniline (0.2 mmol), pepsin (30 mg), and 50% aqueous methanol solution (2 mL), stirred at 60 ℃ for 36 h. Isolated yield.

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•