An efficient trans-diastereo- and enantioselective synthesis of α-substituted β-formyl δ-lactones 5 (de ≥ 98%, ee = 80-95%) is described, employing formaldehyde-SAMP-hydrazone (1) as a neutral formyl anion equivalent. The new procedure involves the Michael addition of 1 to 5,6-dihydro-2H-pyran-2-one (2) followed by trans-selective α-alkylation and subsequent oxidative cleavage of the auxiliary.
描述了一种高效的反式-二歧异构体和对映选择性合成α-取代的β-甲酰δ-内酯5(去对映体≥98%,对映体过剩率=80-95%),该方法采用
甲醛-
SAMP-
肼酮(1)作为中性甲酰阴离子等效物。新程序涉及1与5,6-二氢-
2H-吡喃-2-酮(2)的迈克尔加成,然后进行反式选择性的α-烷基化和随后的辅助体氧化裂解。