5, 1H, H-2), 3.72 (s, 3H, OCH 3), 3.93 (s, 1H, H-1), 5.30 (bs, 1H, CONH), the remaining signals overlap with the signals of (2 S ,1 S ,3 S )-1c; 13C NMR (from diastereomeric selleck compound mixture, CDCl3, 125 MHz): (2 S ,1 S ,3 S )-1c (major isomer): δ 11.3, 15.6 (CH3, \( C\textH_3^’ \)), 25.3 (CH2), 28.6 (C(CH3)3), 38.0 (CH), 50.9 (C(CH3)3), 51.5 (OCH3), 63.5 (C-2), 66.6 (C-1), 127.9 (C-2′, C-6′),
128.2 (C-4′), 128.8 (C-3′, C-5′), 138.8 (C-1′), 170.9 (CONH), 174.7 (COOCH3); (2 S ,1 R ,3 S )-1c (minor isomer): δ 11.7, 16.4 (CH3, \( C\textH_3^’ \)), 25.0 (CH2), 28.8 (C(CH3)3), 38.5 (CH), 50.7 (C(CH3)3), 51.7 (OCH3), 65.3 (C-2), 67.1 (C-1), 127.2 (C-2′, C-6′), 128.0 (C-4′), 128.8 (C-3′, C-5′), 139.6 (C-1′), 171.0 (CONH), 174.7 (COOCH3); HRMS (ESI) calcd for C18H28N2O3Na: 357.2154 (M+Na)+ found 357.2148. Pale-yellow oil; IR (KBr): 700, 754, 1223, 1454, 1516, 1680, 1738, 2872, 2966, 3326; TLC (PE/AcOEt 3:1): R f = 0.20 (major isomer) and 0.24 (minor isomer); 1H NMR (from diastereomeric mixture, CDCl3, 500 MHz): (2 S ,1 S )-1d (major isomer): δ 1.28 (s, 9H, C(CH 3)3), 2.33 (bs, 1H, NH), 2.85 (dd, 2 J = 13.5, 3 J = 8.0, 1H, CH 2), 3.03 (dd, 2 J = 13.5, 3 J = 6.0, 1H, \( \rm CH_2^’ \)), 3.36 (dd, 3 J = 8.0, 3 J = 6.0, 1H, H-2), 3.68 (s, 3H, OCH 3), 4.08 (s, 1H, H-1), 6.67 (bs, check details 1H, CONH), 7.06 (m,
2H, H–Ar), 7.10 (m, 2H, H–Ar), 7.21–7.37 (m, 6H, H–Ar); (2 S ,1 R )-1d (minor isomer): δ 1.08 (s, 9H, C(CH 3)3), 2.68 (dd, 2 J = 13.5, 3 J = 10.0, 1H, CH 2), 3.47 (dd, 3 J = 10.0, 3 J = 4.0, 1H, H-2), 3.75 (s, 3H, OCH 3), 3.96 (s, 1H, H-1), 6.78 (bs, Tacrolimus (FK506) 1H, CONH), the remaining signals overlap with the signals of (2 S ,1 S )-1d; 13C NMR (from diastereomeric mixture, CDCl3, 125 MHz): (2 S ,1 S )-1d (major isomer): δ 28.6 (C(CH3)3), 39.4 (CH2), 50.8 (C(CH3)3), 51.9 (OCH3), 60.4 (C-2), 66.4 (C-1), 126.8 (C-4″), 127.6 (C-2′, C-6′), 128.1 (C-4′), 128.5 (C-2″, C-6″), 128.7 (C-3′, C-5′), 129.3 (C-3″, C-5″), 137.0 (C-1″), 138.4 (C-1′), 170.7 (CONH), 174.1 (COOCH3); (2 S ,1 R )-1d (minor isomer): δ 28.4 (C(CH3)3), 40.2 (CH2), 50.3 (C(CH3)3), 52.1 (OCH3), 62.4 (C-2), 66.8 (C-1), 127.0 (C-4″), 127.2 (C-2′, C-6′), 128.1 (C-4′), 128.7 (C-2″, C-6″), 128.8 (C-3′, C-5′), 129.5 (C-3″, C-5″), 137.6 (C-1″), 139.5 (C-1′), 170.5 (CONH), 174.8 (COOCH3); HRMS (ESI+) calcd for C22H28N2O3Na: 391.1998 (M+Na)+ found 391.1995.