Ge. Keck et al., SYNTHETIC STUDIES ON THE RHIZOXINS .1. 2 STEREOSELECTIVE ROUTES TO A FUNCTIONALIZED C1-C-9 SUBUNIT, Journal of organic chemistry, 58(15), 1993, pp. 3787-3788
Two syntheses of a potential C1-C-9 subunit of rhizoxin are described.
In the first, chelation-controlled allylstannane addition to opticall
y pure aldehyde 3, conversion to unsaturated ester 7, and stereoselect
ive intramolecular Michael addition is used to establish the relative
stereochemistry at C-7 and C-8 (rhizoxin numbering). In the second, an
Evans aldol condensation is used to control absolute and relative ste
reochemistry at these centers. Both approaches use thermodynamic contr
ol to establish the correct stereochemistry at C5.