Synthesis of the Salicylihalamide Core Structure from Epichlorohydrin– Laying the Foundation to Macrolactone Collections

Starting from ( R )‐epichlorohydrin, two successive carbon–carbon bond formations, one with acetylide and the other with cyanide, led to the 3‐hydroxynitrile 20 . This compound was further elaborated to the enynol 29 via an Evans aldol reaction of the derived aldehyde 22 with the pentenoyloxazolidinone 23 and conversion of the carboxyl to a methyl group after the aldol reaction. Mitsunobu esterification of the enynol 29 with the benzoic acid 5 gave rise to the ester 30 with two double bonds and one triple bond. After protection of the terminal triple bond with a TIPS group, the ring closing metathesis proceeded in good yield. The macrolactone E ‐33 was converted into the vinyl iodide 34 and the pyridin containing salicylihalamide analog 36 . The described sequence, the two‐sided elongation of epichlorohydrin appears as a general route to secondary alcohols that can be further elaborated to functionalized macrolactones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)