F13459, a new derivative of mycophenolic acid - II. Physico-chemical properties and structural elucidation

F13459 is a new inhibitor of synthesis and trafficking of virus glycoprotei n isolated from the culture broth of a Penicillium sp. The molecular formul a of F13459 was determined to be C27H28O11 by HRFAB-MS and NMR spectral ana lyses. The structure of F13459 was elucidated to be 3,4-dihydro-3,4,6,8-tet rahydroxy-3-methyl-1H-2-benzopyran-1-one 4-O-mycophenolate, an ester deriva tive of mycophenolic acid. F13459 was isolated as the optically inactive fo rm. F13459 exists in epimeric mixtures at C-3' through relatively fast hemi acetal-ketone tautomerism and at C-4' through slow keto-enol tautomerism. T hose epimerizations were confirmed by NOE differential experiments for fast chemical exchange and equilibrium and by deuteration experiments in NMR fo r slow chemical exchange.