Regioselectivity-reversal in acylation of 6-azauridine catalyzed by Burkholderia cepacia lipase

3′-O-Stearoylation of 6-azauridine was achieved enzymatically for the first time. Among eight commercially available lipases, that from Burkholderia cepacia displayed a 3′-regioselectivity of 80% towards the acylation of 3-hydroxyl of 6-azauridine. Using an immobilized lipase from Burkholderia cepacia, the 3′-regioselectivities of the acylations could be reversed by lengthening the aliphatic chain of the acyl donors (C2–C18). The possible reason might be the presence of the interaction between the base moiety and the acyl group.