Applications of crotyldiisopinocampheylboranes in synthesis: a formal total synthesis of (+)-calyculin A

The formal total synthesis of the marine metabolite (+)-calyculin A is reported. The key steps involve (i) the use of Brown allylboration chemistry to control the relative and absolute stereochemistry of homoallylic alcohol arrays, thus setting eight of the desired stereocenters; (ii) Stille coupling methodology in the construction of the cyano tetraene unit of the natural product; and (iii) a modified Cornforth-Meyers approach to the synthesis of the oxazole fragment.