Using the readily accessible chiral auxiliaries 1–3 the sulfonamide-shielded O-silylated esters 5 underwent π-face-selective α-acetoxylation on successive treatment with Pb(OAc)4 and NEt3 HF to give after recrystallization α-acetoxy ester 6 in 55–67% yields and in 95–100% d.e. Starting from conjugated enoates addition of RCu and subsequent acetoxylation 101112 yielded α,β-bifunctionalized esters 12
使用容易获得的手性助剂1 - 3的磺酰胺的屏蔽ö -silylated酯5例行π面选择性α-乙酰氧基化与
铅(OAC)连续处理4和净3 HF再结晶α乙酰氧基酯后,得到6在55-67%的产率和在95-100%去自共轭enOAtes加成RCU的和随后的
乙酸化起始10 11 12产生了α,β-双官能酯12具有>在两个ç95%的构型控制α和C β。辅助部件的无损拆卸(6 7,6 8和12 13)得到高对映体纯度的α-羟基
羧酸或末端α
-二醇。所制备的二醇8c和13a分别是先前报道的
天然产物16和17的合成的关键中间体。