The chiral reagents (+)- and (−)-(Ipc)2BOTf are used to control the aldol addition reactions of ethylketone3 with methacrolein. Under suitable conditions, racemic3 can be converted into the SS aldol adduct (+)-4 in ≥95% ee with >95% diastereoselectivity. Resolved starting ketone (+)-3 can be recovered in ≥95% ee. Adduct (+)-4 was converted into the rifamycin S segment (−)-2via stereoselective ketone
手性试剂(+)-和(-)-(Ipc)2 BOTf用于控制乙基酮3与甲基
丙烯醛的羟醛加成反应。在合适的条件下,外消旋3可以在≥95%ee的情况下以> 95%的非对映选择性转化为SS羟醛加合物(+)- 4。分离的起始酮(+)- 3可以在≥95%ee中回收。通过立体选择性酮还原和
硼氢化,将加合物(+)- 4转化为
利福霉素S片段(-)- 2。