3 (C-1), 127.6 (C-2′, C-6′, C-2″, C-6″), 128.5, 128.6 (C-4′, C-4″), 129.0 (C-3′, C-5′, C-3″, C-5″), 137.1, 138.3 (C-1′, C-1″), 172.6 (CONH), 174.3 (COOCH3); (2 S ,1 R )-2e (minor isomer): δ 52.5 (OCH3), 63.5 (C-2), 65.3 (C-1), 127.4, 127.7 (C-2′, C-6′, C-2″, C-6″), 128.4, 128.5 (C-4′, C-4″), 128.9, 129.0 (C-3′, C-5′, C-3″, C-5″), 137.3, 138.1 (C-1′, C-1″), 173.0 (CONH), 174.4 (COOCH3); HRMS (ESI+) calcd for C17H18N2O3Na: 321.1215 (M+Na)+ found 321.1227. Methyl (+/−)-2-(2-benzyl-2-amino-2-oxo-1-phenylethylamino)-acetate

rac -2f From rac -1f (0.59 g, 1.60 mmol) and BF3·2CH3COOH (5 mL); FC (gradient: PE/AcOEt 4:1–1:2): yield 0.40 g (80 %) of rac -2f. White powder; mp 147–149 °C; TLC (AcOEt): R f = 0.63; IR (KBr): 700, 741, 1204, 1454, 1558, 1682, 1734, 2844, 2951, 3030, 3182, 3418; 1H NMR Selleckchem GSK3326595 (CDCl3, 500 MHz): δ 3.07 (d, 2 J = 17.5, 1H, PhCH 2), 3.40 (d, 2 J = 17.5, 1H, Ph\( \rm CH_2^’ \)), 3.61 (s, 3H,

OCH 3), 3.66 (d, 2 J = 13.5, 1H, CH 2), 3.85 (d, 2 J = 13.5, 1H, \( \rm CH_2^’ \)), 4.75 (s, 1H, H-1), 5.85 (bs, 1H, CONH), 7.26–7.42 AR-13324 (m, 10H, H–Ar), 7.63 (bs, 1H, CONH′); 13C NMR (CDCl3, 125 MHz): δ 51.7 (OCH3), 51.8 (PhCH2), 56.8 (CH 2), 69.9 (C-1), 127.7, 128.4 (C-4′, C-4″), 128.64, 128.65 (C-2′, C-6′, C-2″, C-6″), 129.0, 129.6 (C-3′, C-5′, C-3″, C-5″), 134.7, 137.5 (C-1′, C-1″), 172.3 (CONH), 174.4 (COOCH3); HRMS (ESI+) calcd for C18H20N2O3Na: 335.1360 (M+Na)+ found 335.1372. Synthesis of compounds 3 by base-induced intramolecular cyclocondensation To a stirred solution of appropriate selleck inhibitor amidoester 2 in absolute EtOH (5 mL/1 mmol of amidoester), sodium hydroxide (1 equiv.) was added at room temperature. After dissolution Atazanavir of the hydroxide, the mixture was quenched with saturated aqueous solution of ammonium chloride (100 mL). The resulting cloudy solution was extracted with CH2Cl2 (3 × 30 mL). The combined organic phase was washed with water (20 mL), dried over anhydrous MgSO4, filtered and concentrated under reduced pressure. The residue was purified by FC. (3S,5R)- and (3S,5S)-3-isopropyl-5-phenylpiperazine-2,6-dione

(3 S ,5 S )-3a and (3 S ,5 R )-3a From (2 S ,1 S )-2a (1.86 g, 7.04 mmol) and NaOH (0.28 g, 1 equiv.); FC (gradient: PE/EtOAc 6:1–1:1): yield 1.34 g (82 %): 0.72 g (44 %) of (3 S ,5 S )-3a, 0.32 g (19 %) of (3 S ,5 R )-3a and 0.30 g (19 %) of diastereomeric mixture. (3 S ,5 S )-3a: white powder; mp 103–105 °C; [α]D = −152.1 (c 1, CHCl3); IR (KBr): 756, 1030, 1099, 1180, 1234, 1331, 1454, 1497, 1701, 2932, 1963, 3225; TLC (PE/AcOEt 3:1): R f = 0.35; 1H NMR (CDCl3, 500 MHz): δ 0.99 (d, 3 J = 7.0, 3H, CH 3), 1.09 (d, 3 J = 7.0, 3H, \( \rm CH_3^’ \)), 2.18 (bs, 1H, NH), 2.49 (2 sp, 3 J 1 = 6.5, 3 J 2 = 5.0, 1H, CH), 3.26 (d, 3 J = 4.5, 1H, H-3), 4.90 (s, 1H, H-5), 7.32–7.46 (m, 5H, H–Ar), 8.34 (bs, 1H, CONHCO); 13C NMR (CDCl3, 125 MHz): δ 17.1 (CH 3), 19.3 (CH 3), 27.7 (CH), 58.7 (C-3), 59.8 (C-5), 127.1 (C-2′, C-6′), 128.5 (C-4′), 129.0 (C-3′, C-5′), 134.6 (C-1′), 172.3 (C-6), 173.