Versatile 8-oxabicyclo[3.2.1]oct-6-en-3-one: stereoselective methodology for generating C-glycosides, delta-valerolactones, and polyacetate segments.

[figure: see text] A new rearrangement of functionalized methoxy glycosides and a regioselective as well as stereoselective intramolecular Michael addition giving delta-valerolactones and C-glycosides are described. Applications to the synthesis of marine natural products are reported. Chemoselective deprotection of benzylated hydroxy groups is assumed to be facilitated by 6-endo-tet interaction with the 1,3-dithiane functionality.