Formal Total Synthesis of Amphidinolide Q

Abstract

With the preparation of macrolactone 33a we describe a formal total synthesis of amphidinolide Q. The corresponding seco acid 32 originated from an aldol reaction between methyl ketone 6 and methyl (E)-3-methyl-4-oxobut-2-enoate (5). The synthesis of ketone 6 (C5-C16 fragment) started with desymmetrized meso-diol 9. Chain extension reactions involving cyanide, lithium trimethylsilylacetylide, and a Wittig reaction led to aldehyde 22. The two additional stereocenters at C11 and C13 were set by a Noyori transfer hydrogenation on alkynone 14 and a Feringa-Minnaard methyl cuprate addition on enoate 21. The but-1-ene-2-yl subunit on the side chain terminus was created from an unsaturated aldehyde by a substitution reaction on a derived allylic tosylate.