Remarkable long range effects on the diastereoface selectivity in an aldol condensation

The stereochemical results in an aldol reaction between the enolate 2 and various α-methyl aldehydes indicates a stabilizing through space interaction between C4C5 unsaturation and the formyl group. This interaction leads to a reaction conformation which favors a C7C8 (epothilone numbering) anti-relationship in the aldol products. Included is an extensive study that identifies steric and electronic effects of various α-methyl aldehydes in the aldol diastereoselection.