A stereoselective process for chiral intermediates to 1-carbapenum and 1-carbacephalosporins is provided comprising the use of an N-acyl-(4R)-substituted-1,3-thiazolidine-2-thione as a chiral auxiliary in boron enolate mediated aldol condensation with a protected-.beta.-keto ester aldehyde. E.g., benzyl 3,3-(ethylenedioxy)-4-formylbutyrate is condensed with the boron enolate formed with n-butyryl (4R)-methoxycarbonyl-1,3-thiazolidine-2-thione to provide benzyl 3,3-ethylenedioxy-(5R)-hydroxy-6-[(4R)-methoxycarbonyl-1,3-thiazolidine-2- thione-3-ylcarbonyl]octanoate. Displacement of the thiazolidine-2-thione chiral auxiliary moiety with an O-alkyl, O-acyl or O-aralkyl hydroxyamine provides the corresponding chiral intermediate as the hydroxamate.
提供了一种对手性中间体制备1-碳青霉烯和1-碳
头孢菌素的立体选择性过程,包括在
硼酸烯醇介导的保护的β-
酮酯醛的醛缩反应中使用N-酰基-(4R)-取代-1,3-
噻唑烷-2-
硫酮作为手性辅助剂。例如,
苯甲酸苄酯和n-丁酰(4R)-甲氧羰基-1,3-
噻唑烷-2-
硫酮形成的
硼烯醇缩合反应,得到
苯甲酸苄酯3,3-乙二氧基-(5R)-羟基-6-[(4R)-甲氧羰基-1,3-
噻唑烷-2-
硫酮-3-基]
辛酸酯。用O-烷基、O-酰基或O-芳基
羟胺取代
噻唑烷-2-
硫酮手性辅助基团,得到相应的手性中间体
羟胺盐。