Synthesis of a sec-precursor and analogues of macrolactin A

A highly convergent and efficient route to sec-precursor 26 of macrolactin A has been developed. In the synthesis, Wittig and Horner-Emmons reactions were utilized to construct the conjugated dienes and control the right configurations of E,Z-and E,E-dienes. The segment 2 and 3 were prepared from the known compound 4 and 15 respectively. The coupling of segments 2 and 3 proceeded in the presence of NaHMDS. The analogues 7 and 32 were synthesized by the same strategy.