Crystalline 5-O-acetyl-2,3-isopropylidenedioxy-d-ribonolactone oxime (8) was synthesised from d-ribose in 40% overall yield. The chloronitroso dienophile 3b was obtained from 8 by oxidation with t-BuOCl and underwent asymmetric Diels-Alder reaction with cyclic and acyclic dienes 10-13 to give crystalline adducts 14a-17a in good yield and excellent enantiomeric excess (93-99%).
晶体形式的5-O-乙酰基-2,3-异丙基二氧基-d-
核糖内酯
肟(8)通过从d-
核糖合成,整体产率为40%。
氯亚硝基二烯亲电试剂3b是通过t-BuOCl氧化8得到的,并与环状和非环状二烯10-13进行了不对称Diels-Alder反应,生成了晶体加合物14a-17a,产率良好且光学纯度极高(93-99%)。