A new and efficient asymmetric synthesis of an A-ring precursor to physiologically active 1.alpha.-hydroxyvitamin D3 steroids
摘要:
A highly stereocontrolled and mild Diels-Alder cycloaddition involving stereochemically matched pyrone (S)-lactate 4 and Lewis acid (-)-Pr(hfc)3 produced bicyclic lactone endo-5 via a double stereodifferentiation process. Bicyclic lactone 5 was then transformed smoothly and in high yield into phosphine oxide (-)-1, an important A-ring precursor to various physiologically active 1alpha-hydroxyvitamin D3 steroids.
A new and efficient asymmetric synthesis of an A-ring precursor to physiologically active 1.alpha.-hydroxyvitamin D3 steroids
摘要:
A highly stereocontrolled and mild Diels-Alder cycloaddition involving stereochemically matched pyrone (S)-lactate 4 and Lewis acid (-)-Pr(hfc)3 produced bicyclic lactone endo-5 via a double stereodifferentiation process. Bicyclic lactone 5 was then transformed smoothly and in high yield into phosphine oxide (-)-1, an important A-ring precursor to various physiologically active 1alpha-hydroxyvitamin D3 steroids.