Highly Stereodivergent Approach to Both Enantiomers of 4-Substituted β-Lactams via Diastereofacially Controlled Addition of Enolates of<i>t</i>-Butyl Acetate to a Chiral Imine
作者:Makoto Shimizu、Yutaka Ukaji、Junko Tanizaki、Tamotsu Fujisawa
DOI:10.1246/cl.1992.1349
日期:1992.7
Addition of lithium or triisopropoxytitanium enolate derived from t-butyl acetate to a chiral imine possessing dioxolane ring as a chiral auxiliary gave (3S)-β-amino ester exclusively, whereas chlorozinc enolate underwent re-facial attack to give (3R)-isomer with good selectivity. The β-amino esters thus obtained were readily converted to the corresponding (4S)- and (4R)-β-lactams respectively without loss of the stereochemical integrity at C-4 of the β-lactam rings.
将从叔丁基乙酸酯衍生的锂或三异丙氧基钛烯醇盐与具有二氧杂环作为手性辅助基团的手性亚胺反应,得到(3S)-β-氨基酯,而氯锌烯醇盐则发生了再面进攻,选择性较好地生成(3R)-异构体。由此获得的β-氨基酯可以在不损失β-内酯环C-4立体化学完整性的情况下,方便地转化为相应的(4S)-和(4R)-β-内酯。