名称:
[2+2]cycloaddition of chlorosulfonyl isocyanate to (Z) 3-O-(2′-silylvinyl) ethers of 1,2-O-isopropylidene-5-O-trityl-α-D-xylofuranose
摘要:
The asymmetric [2+2]cycloaddition of chlorosulfonyl isocyanate to 1,2-O-isopropylidene-3-O-2'-silylvinyl)-5-O-trityl-alpha-D-xylofuranose proceeds with high steroselectivity in a good yield to afford the corresponding azetidin-2-ones with (R) configuration at the newly formed stereogenic center. The bulky t-butyl-dimethyisilyl substituent causes partial epimerization at C-3' carbon atom of the azetidin-2-one ring. Intramolecular alkylation of the nitrogen atom by the terminal carbon of the sugar chain gives 1-oxacephams; basic conditions of cyclization cause desilylation or partial desilylation of products. (C) 1998 Elsevier Science Ltd. All rights reserved.
DOI:
10.1016/s0040-4020(98)00857-6