名称:
Stereocontrolled synthesis of a trihydroxylated A ring as an immediate precursor to 1.alpha.,2.alpha.,25-trihydroxyvitamin D3
摘要:
3-Bromo-2-pyrone (1) was coaxed into inverse-electron-demand Diels-Alder cycloaddition with dioxole 2 under sufficiently mild thermal conditions to allow isolation of functionally and stereochemically rich bicycloadduct endo-3 that was transformed into trihydroxylated A-ring allylic phosphine oxide as an immediate precursor to 1-alpha,2-alpha,25-trihydroxyvitamin D3.