Ma. Soler et al., STEREOCONTROLLED SYNTHESIS OF CYCLIC ETHERS BY INTRAMOLECULAR HETERO-MICHAEL ADDITION .4. ENANTIOMERIC SYNTHESIS OF SUBSTITUTED AND FUSED OXEPANES, Tetrahedron letters, 34(34), 1993, pp. 5471-5474
The use of an intramolecular hetero-Michael addition of enantiomerical
ly enriched 7-alkoxy4-benzoyloxy-2,3-unsaturated esters for the synthe
sis of endo-substituted oxepanes is described, The stereochemistry in
the cyclization step is governed by the geometry of the double bond in
the unsaturated ester and the presence of a Z-double bond in the line
ar chain is required in order to achieve good yields. The synthesis of
the fused oxepane-tetrahydropyran nucleus of marine polyether toxins
with absolute control of all the stereocentres is described.