Two new approaches to the 25-hydroxy-vitamin D2 side chain
作者:Stephen R. Wilson、Andrew E. Davey、Maria E. Guazzaroni
DOI:10.1021/jo00033a021
日期:1992.3
Two approaches to the 25-hydroxy-vitamin D2 side chain have been developed based on the solvolysis of cyclopropylcarbinyl precursors. The first involves addition of trimethylcyclopropyllithium reagent 4 to a suitably protected C/D system 9. This reaction leads directly to cyclopropylcarbinols 10a,b which can be solvolyzed to the vitamin D2 side chain directly. The second approach uses an intermediate C/D system with a side chain allylic alcohol. Cyclopropanation of the allylic alcohol using Et2Zn/CH3CHI2 produces the same type of cyclopropylcarbinols 10a,b but in differing isomer ratios. Model studies and stereochemical differences in the two approaches are discussed.
An efficient synthesis of the 25-hydroxy Windaus–Grundmann ketone
作者:Yagamare Fall、Cristian Vitale、Antonio Mouriño
DOI:10.1016/s0040-4039(00)01224-7
日期:2000.9
A short and efficientsynthesis of the 25-hydroxy Windaus–Grundmann ketone from the Inhoffen–Lythgoe diol is described (seven steps, 70% overall). The most relevant feature of the synthesis is the preparation of the Wittig reagent 3 from cheap and commercially available starting materials. Pure 3 can be obtained in multigram quantities for achieving clean and efficient Wittig reactions.