SYNTHESIS OF THE PAPULACANDIN C-ARYLGLUCOSYL SPIROKETAL NUCLEUS

The enantiomerically pure tricyclic C-arylglucosyl spiroketal nucleus of papulacandin has been synthesized by reaction of an appropriately protected gluconolactone 4 with a metalated derivative of 5-(hydroxymethyl)resorcinol (5). In model studies, alkyllithium and aryllithium reagents reacted with δ-valerolactone (6) and tetra-O-benzylgluconolactone (9) to afford the expected lactols or hydroxy ketones. Furthermore, aryllithium reagent 14a reacted with-valerolactone to afford spiroketal 15a. Aryllithium reagent 14a reacted with tetra-O-benzylgluconolactone (9) to give a mixture of epimeric spiroketals 16a and 17. More satisfactorily, aryllithium reagent 14b reacted with 9 to provide hydroxy ketone 19a which was deprotected and cyclized to afford 16c, the C-arylglucosyl spiroketal nucleus of papulacandin. A procedure has been developed for acylation at 0-3. © 1990, American Chemical Society. All rights reserved.