An efficient synthesis of epothilone D analogs of type 1 has been developed, which is based on a highly diastereoselective Evans aldol reaction as one of the key steps. A profound difference in the relative stabilities of TBS-protecting groups on C7-O and C15-O was observed between secondary and primary amide groups at C5-N4. Although modeling studies had suggested analogs of type 1 to assume a conformation similar to the NMR-derived conformation of tubulin-bound epothilone A, compounds 1a-d were found to be significantly less active than the parent compound epothilone D.