hetero-Michael (DIHMA) reaction to alkynones was applied. The sequence allows for introduction of numerous substituents on the scaffold and for variation of stereochemistry. [5.5]-Spiroketals bearing an additional ketone were obtained in high overall yields. Further diversification was achieved by reduction of the ketone and reductive amination using polymer-supported borohydride, Grignard reaction and conversion
Stereoselective Synthesis of the Tetrahydropyran Core of Polycarvernoside A
作者:Conor S. Barry、Nick Bushby、John R. Harding、Christine L. Willis
DOI:10.1021/ol050840o
日期:2005.6.1
[reaction: see text] A concise and stereoselectivesynthesis of the tetrasubstituted tetrahydropyran core of polycavernoside A was achieved in 55% overall yield from 3-benzyloxypropanal. A stereoselective allyl transfer reaction was used in the synthesis of enol ether 18 followed by a TFA-mediated cyclization to create the three new asymmetric centers in the tetrahydropyran with complete stereocontrol in