Biocatalytic deacylation studies on tetra-O-acyl-β-D-xylofuranosyl nucleosides: synthesis of xylo-LNA monomers.

A Novozyme-435 catalytic methodology has been developed for selective deacylation of one of the acyloxy functions involving a primary -OH group over the other acyloxy functions involving primary and secondary -OH groups in 4'-C-acyloxymethyl-2',3',5'-tri-O-acyl-β-D-xylofuranosyl nucleosides. Optimization of the biocatalytic reaction revealed that tetra-O-butanoyl-β-D-xylofuranosyl nucleosides are the best substrates for the enzyme. The possibility of acyl migration during enzymatic deacylation reactions has been ruled out by carrying out biocatalytic deacylation reactions on mixed esters of 4'-C-hydroxymethyl-2',3',5'-tri-O-acetyl-β-D-xylofuranosyl nucleosides. The developed methodology has been used for the efficient synthesis of xylo-LNA monomers T, U, A, and C in good yields.