(±)-spiro-γ-lactone 1 lithium enolate (3 equiv) by the O-TBDMS methyl (−)-(S)-lactate, the O-TBDMS methyl (+)-(S)-mandelate, or the diacetone-d-glucose carbonate (1 equiv each) occurs with a kinetic resolution. The (S,S)-enolate is the most reactive with the lactate and it is the (R,R)-enolate, which selectively reacts with the mandelate or the DAG carbonate. After alkylation of the resulting acyl lactones
O -TBDMS甲基(-)-(S)-乳酸,O -TBDMS甲基(+)-(S)-扁桃酸酯对(±)-螺-γ-内酯1烯醇锂(3当量)的酰化作用或diacetone- d葡萄糖碳酸酯(1当量各)发生与动力学拆分。(S,S)烯酸酯与乳酸的反应性最强,它是(R,R)-烯酸酯,其与扁桃酸酯或DAG碳酸盐选择性反应。用4-或5-甲氧基-1-碘苯并环丁烯烷基化所得的酰基内酯并加热后,得到标题化合物,并且在脱保护后,通过单晶X射线分析确定光学纯的新类固醇的结构。
Highly Stereoselective Alkylation of Spiro-γ-lactones
The alkylation of the (+/-)-spiro-gamma-lactones 1 and 5a occurs with high diastereofacial selectivity. Geometry-optimized ab initio 4-31G calculations on enol 7 suggest that electrophilic attack occurs at an angle of about 80 degrees to the plane of the enolate, together with a displacement of the trajectory away from the oxygen linked to lithium.
A five step synthesis of (d,l)-estrane derivatives from 1,3-butadiene