Lewis Acid-Promoted, Stereocontrolled, Gram Scale, Diels−Alder Cycloadditions of Electronically Matched 2-Pyrones and Vinyl Ethers: The Critical Importance of Molecular Sieves and the Temperature of Titanium Coordination with the Pyrone
作者:Gary H. Posner、Haiyan Dai、D. Scott Bull、Jae-Kyoo Lee、Franck Eydoux、Yuji Ishihara、William Welsh、Neil Pryor、Stan Petr
DOI:10.1021/jo9515900
日期:1996.1.1
enantiocontrolled Diels-Alder cycloadditions with electron-rich vinyl ether CH(2)=CHOCH(2)-1-naphthyl and vinyl silyl ether CH(2)=CHOSiMe(2)Bu-t leading to valuable 1alpha,25-dihydroxyvitamin D(3) (calcitriol) intermediate (-)-2. Unexpectedly, two subtle variables were found to be critical for obtaining reproducibly over 90% enantioselectivities in gram scale cycloadditions: (1) the moisture content (15-17%
A new and efficient asymmetric synthesis of an A-ring precursor to physiologically active 1.alpha.-hydroxyvitamin D3 steroids
作者:Gary H. Posner、Jean Christophe Carry、Tizah E. N. Anjeh、Andrew N. French
DOI:10.1021/jo00052a007
日期:1992.12
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.
POSNER, GARY H.;KINTER, CHRIS M., J. ORG. CHEM., 55,(1990) N3, C. 3967-3969
作者:POSNER, GARY H.、KINTER, CHRIS M.
DOI:——
日期:——
Asymmetric total synthesis of an A-ring precursor to hormonally active 1.alpha.,25-dihydroxyvitamin D3
作者:Gary H. Posner、Chris M. Kinter
DOI:10.1021/jo00300a001
日期:1990.6
Binaphthol-titanium-promoted, highly enantiocontrolled, Diels-Alder cycloadditions of electronically matched 2-pyrones and vinyl ethers: Streamlined asymmetric synthesis of an A-ring precursor to physiologically active 1α-hydroxyvitamin D3 steroids
作者:Gary H. Posner、Franck Eydoux、J.K. Lee、D.Scott Bull
DOI:10.1016/s0040-4039(00)78338-9
日期:1994.10
Bicyclic lactones 4, A-ringprecursors to diverse physiologically active 1α-hydroxyvitamin D3 analogs, were prepared in excellent yields and enantiomeric purities via chiral, non-racemic Lewis acid-promoted, mild, inverse-electron-demand 4+2-cycloadditions.