Synthetic studies of the spirocyclic cyclohexene part of versipelostatin, a novel GRP78/Bip molecular chaperone downregulator

The spirocyclic part consisting of an α-acylated tetronic acid and a multisubstituted cyclohexene embedded in versipelostatin, a novel GRP78/Bip molecular chaperone downregulator, has been synthesized in enantiomerically pure form. The asymmetric synthesis of the targeted spiro[4.5]-1-oxa-7-decen-2,4-dione derivative was characterized by (1) stereoselective allylation at the α-carbon of methylmalonate diester, in which one carboxylic acid was esterified with a D-glucose-derived chiral template, (2) construction of the tetrasubstituted cyclohexenone substructure by high-yielding ring-closing metathesis and (3) stereoselective construction of the spirocyclic tetronic acid part starting from the cyclohexenone obtained as the ring-closing metathesis product.