Nitrogen → HCID 18667335, compound

Participants

Reaction Steps

N-(N-Benzyloxycarbonyl-(S)-valinyl-(S)-alaninyl)-3-amino-4-(2-benzoxazolyl)-4-oxobutanoate (63; Q). A solution of the ester 62 (95.0 mg, 0.16 mmol) in a 1:1 mixture of methylene chloride and trifluoroacetic acid (10.0 ml) was stirred for 1 h under a dry atmosphere of N2. The solution was then reduced in vacuo, taken up in ether and reduced again. This process was repeated six times to afford the crude product as an off white solid. Flash chromatography (95:5 methylene chloride/methanol) gave 60.0 mg (69%) of the title compound as a white solid. The product existed as a mixture of three isomers in CD3OD, consisting of the ketone form (one isomer, c 44%), and its acycloxy ketal form (two isomers at C-4, c. 56%): m.p. 156°-159° C. [α]D26 -45.6° (c 0.13, methanol); IR (KBr) 3440, 2967, 1713, 1703, 1638, 1531, 1427; 1H NMR (CD3OD) δ 7.93-7.24 (9H, m), 5.59 (1H, brt), 5.16-5.00 (2H, m), 5.0-4.78 (1H, m), 4.50-4.22 (1H, m), 3.95-3.81 (1H, m), 3.11 (2H, d, J=6.5), 3.05-2.92 (1H, m), 2.70-2.39 (1H, m), 2.08-1.89 (1H, m), 1.19-0.78 (9H, m). Anal. Calcd. for C27H30N4O8. 0.5H2O: C, 59.22; H, 5.71; N, 10.23. Found: C, 59.48, H, 5.36, N, 10.17. M.S. (+FAB); 539 (M+ +1), 91. ##STR114## (a) R1 =OCH3, R2 =H (b) R1 =H, R2 =OCH3

Provenance & Evidence