Oxetane δ‐Amino Acids: Chemoenzymatic Synthesis of 2,4‐Anhydro‐5‐N‐(t‐butoxycarbonyl)amino‐D‐lyxonic Acid
摘要:
Starting from 1,2-O-isopropylidene-D-xylose, methyl 2,4-anhydro-3,5-di-O-benzyl-D-lyxonate ( 4) was synthesized. Debenzylation and transformation of the primary hydroxyl group yielded methyl 2,4-anhydro-5-N-(t-butoxycarbonyl)amino-D-lyxonate (9). While transesterification of 4 under basic reaction conditions was straightforward, an analogous reaction with 9 was not successful. After screening of several lipases, the enzymatic transesterification of 9 was achieved with lipase L2 from Candida antarctica to furnish the title compound 2,4-anhydro-5-N-(t-butoxycarbonyl)amino-D-lyxonic acid in excellent yield. The stereochemistry at the oxetane ring was proven by an x-ray structure of the intermediate methyl 2,4-anhydro-5-azido-D-lyxonate.[GRAPHICS]
Ring contraction reactions of 2-O-methanesulfonates of α-hydroxy-γ-lactones in aqueous medium to oxetane-2-carboxylic acids: A convenient synthesis of 3′-O-methyloxetanocin and a formal synthesis of oxetanocin
作者:Anil K. Saksena、Ashit K. Ganguly、Viyyoor M. Girijavallabhan、Russell E. Pike、Yao-Tsung Chen、Mohindar S. Puar
DOI:10.1016/0040-4039(93)88027-g
日期:1992.12
thiohydroxamic ester 17 directly provided the key oxetanosyl-thiopyridyl glycosides 18 which were successfully coupled to N-benzoyladenine. A two-step ring contraction of the tosylate 7 to the oxetane-2-carboxamide 23 is described. Attempted ring contraction of the triflate 24 gave the unexpected products 25 and 26. A ringexpansion reaction (e.g. 14a → 21a) was also observed.