Studies on amino acid derivatives. IX. Synthesis of chiral penam-3-carboxylic acid and its substituted derivatives.
作者:Takuo CHIBA、Jun-ichi SAKAKI、Satoshi KOBAYASHI、Toshio FURUYA、Noriyoshi INUKAI、Chikara KANEKO
DOI:10.1248/cpb.37.877
日期:——
Methyl penam-(3S)-carboxylate (methyl 7-oxo-1-thia-4-azabicyclo[3.2.0]heptane-(3S)-carboxylate), the basic skeleton of penicillin-type β-lactams, has been synthesized from D-cysteine methyl ester and tert-butyl formylacetate in three steps through the formation of the thiazolidinylacetic acid followed by cyclization by Mukaiyama-Ohno's procedure. Use of D-penicillamine methyl ester as well as the dimethyl derivative of tert-butyl formylacetate in the above method provides a general synthetic route to a variety of methyl penam-(3S)-carboxylates having methyl groups at the 2 and/or 6-positions.The yields as well as stereoselectivity at C-5 in the cyclization step are shown to be strongly dependent upon the patterns of substituents on the thiazolidinylacetic acid skeleton, and the reason for this is discussed from the mechanistic viewpoint.
青霉素类 β-内酰胺的基本骨架--五南-(3S)-羧酸甲酯(7-氧代-1-硫杂-4-氮杂双环[3.2.0]庚烷-(3S)-羧酸甲酯),是由 D-半胱氨酸甲酯和甲酰乙酸叔丁酯,通过 Mukaiyama-Ohno 程序,先形成噻唑烷基乙酸,再环化,分三步合成的。在上述方法中使用 D-青霉胺甲酯以及甲酰乙酸叔丁酯的二甲基衍生物,为在 2 位和/或 6 位上具有甲基的各种戊-(3S)-羧酸甲酯提供了一条通用的合成路线。研究表明,环化步骤中 C-5 位的产量和立体选择性与噻唑烷基乙酸骨架上的取代基形态密切相关,并从机理的角度讨论了其中的原因。