2-Fluoroalkyl A-ring analogs of 1, 25-dihydroxyvitamin D3. Stereocontrolled total synthesis via intramolecular and intermolecular Diels-Alder cycloadditions. …

…, TEN Anjeh, N Johnson, RL Horst…

Index: Posner, Gary H.; Cho, Cheon-Gyu; Anjeh, Tizah E. N.; Johnson, Neil; Horst, Ronald L.; et al. Journal of Organic Chemistry, 1995 , vol. 60, # 14 p. 4617 - 4628

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Citation Number: 52

Abstract

Intramolecular Diels-Alder (IMDA) cycloadditions of electron-rich trans-vinylic silaketal groups tethered via a chiral, nonracemic 173-butanediol auxiliary to electron-poor 2-pyrone- 3-carboxylates (eg (R)-9,(5'1-14) were promoted by zinc dibromide and proceeded unexpectedly in a stepwise, ionic fashion to form exclusively cis-4, 5-disubstituted bicyclic lactones 10 and 15 with nearly complete asymmetric induction. Confirmation of the ...