2,3-Dideoxy-D-erythro-hex-2-enono-1,5-lactone and 1,4-Lactone Obtained from Tri-O-acetyl-D-glucal

In the 1,5-lactone compound, C 6 H 8 O 4 , the lactone ring adopts a conformation between sofa and half-chair. The five-membered ring in the 1,4-lactone, C 6 H 8 O 4 , is planar and the side chain is in a staggered conformation. The crystal structure of the 1,5-lactone is stabilized by both O-H...O and C-H...O hydrogen bonds and that of the 1,4-lactone by O-H...O hydrogen bonds.