Oxazoline <i>N</i>-Oxide Mediated [2 + 3] Cycloadditions. Application to a Formal Synthesis of (+)-Carpetimycin A
作者:M. Mauduit、C. Kouklovsky、Y. Langlois、C. Riche
DOI:10.1021/ol005596+
日期:2000.4.1
[formula: see text] Cycloaddition between gamma,delta-unsaturated beta-enamino ester 9 and camphor-derived oxazoline N-oxide 8 afforded a single adduct, 14. Dipolarophile 9 proved to be very reactive despite the substitution on the double bond. Stereoselective sodium cyanoborohydride reduction of the imminium intermediate 14a gave rise stereoselectively to beta-amino ester derivative 15a. Oxidative
γ,δ-不饱和β-烯氨基酯9与樟脑衍生的恶唑啉N-氧化物8之间的环加成反应可得到单一的加合物14。尽管在双键上被取代,亲偶极子9仍具有很高的反应活性。亚胺中间体14a的立体选择性氰基硼氢化钠的还原使β-氨基酯衍生物15a立体选择性地产生。氧化性酸性水解,所得醛18的氧化,脱保护和环化后,得到β-内酰胺23,这是(+)-卡比霉素A的直接前体。