The Squalestatins: C-3 Decarboxylation Studies and Rearrangement to the 6,8-Dioxabicyclo(3.2.1)octane Ring System.

3-Decarboxy squalestatins 3 and 4 were synthesised via photolysis of t-butyl peroxyester 7. Lactol 10 was isolated unexpectedly from both HCl-dioxan cleavage of 8, a by-product of the photolysis, and attempted Barton decarboxylation of 6. In TFA under anhydrous conditions, 8 was converted to the tricyclic ether 11.