Relative and absolute configuration of versipelostatin, a down-regulator of molecular chaperone GRP78 expression

structure: see text] Versipelostatin is the first compound which specifically inhibits the expression of GRP78 and the resultant robust cell death under stress conditions, in contrast to the weak cytotoxicity under normal conditions. Versipelostatin consists of a macrocyclic aglycone with an alpha-acyltetronic acid and three sugar moieties. The relative and absolute configuration of the aglycone moiety was established to be 4S, 5S, 6R, 9S, 10S, 13S, 16R, 18R, 19R, 20R, 24R, 27R, and 29S utilizing NMR techniques.