of 3-electron-withdrawing group substituted α-pyrones with α,β-unsaturated hydrazones as electron-rich counterparts are catalyzed by Eu(hfc)3 to afford bicyclic lactone cycloadducts. This is an example of umpolung cycloaddition based on functional transformation of carbonyls to hydrazones. A subsequent dehydrazonation reaction enables indirect synthesis of carbonyl group-containing bicyclic lactones
Stereocontrolled synthesis of highly functionalized cyclohexenes. A short synthesis of a chorismic acid precursor
作者:Gary H. Posner、Todd D. Nelson
DOI:10.1016/s0040-4020(01)85582-4
日期:——
allowing isolation of the structurally and stereochemically rich initial bicyclic adducts 8. These bicyclic adducts are shown to be useful building units as exemplified by a very short and high-yield preparation of a chorismic acid precursor.
Stereocontrolled Total Synthesis of Calcitriol Derivatives: 1,25-Dihydroxy-2-(4'-hydroxybutyl)vitamin D3 Analogs of an Osteoporosis Drug
作者:Gary H. Posner、Neil Johnson
DOI:10.1021/jo00104a050
日期:1994.12
The diastereomeric 2 alpha- and 2 beta-(4'-hydroxybutyl) calcitriol analogs (-)-3 and (+)-3' were prepared in only 11 chemical operations, starting with 4 + 2-cycloaddition of commercially available methyl 2-pyrone-3-carboxylate. Highlights of this convergent and stereocontrolled synthetic approach are as follows: (1) retention of reactant dienophile geometry in the product bicyclic lactone, characteristic of a concerted inverse-electron-demand Diels-Alder cycloaddition; (2) an improved decarboxylation procedure involving chemospecific allyloxide opening of a lactone ring in the presence of a methyl ester and then non-high pressure palladium-promoted allylic ester decarboxylation; and (3) use of the enantiomercially pure C,D-ring chiron (+)-14 to resolve racemic A-ring phosphine oxide (+/-)-13. Relative binding affinities of the enantiomerically pure diastereomers (-)-3 and (+)-3' to the vitamin D binding protein and to the vitamin D receptor showed some unexpected trends. Diastereomer (+)-3' surprisingly bound more effectively to the vitamin D receptor than did the established osteoporosis drug ED-71 (1).
Asymmetric Diels-Alder cycloadditions using chiral alkyl vinyl ethers and a dienyl sulfone
作者:Gary H. Posner、David G. Wettlaufer
DOI:10.1016/s0040-4039(00)84068-x
日期:1986.1
POSNER, G. H.;HARRISON, W.;WETTLAUFER, D. G., J. ORG. CHEM., 1985, 50, N 25, 5041-5044