This method, however, is not always satisfactory in the 3′-O-phosphorylation. In our experience, for instance, sequential treatment of 1 (B = Cy;R = TBDMS) with (1) POCl 3 (2 equiv) in PO(OCH 3 ) 3 at 0 °C for 4 h, (2) H 2 O, overnight, and (3) TBAF (excess) in THF at 25 °C for 1.5 h gave 3 (B = Cy) in only 27% yield (HPLC analysis) together with many side-products. ... No enzymatic 3′-O-phosphorylation methods have been reported.