Partially acetylated sucroses have been prepared by several approaches. They can be synthesized, from trityl ethers and acetals of sucrose, as precursors, by several conventional chemical methodslF3. They can also be prepared by the selective deacylation of peracetylated sucrose, in chloroform solution on aluminium oxide4,', in methanol solution on aluminium oxide impregnated with potassium carbonate 6,7 dissolved in propylamine or isopropylamine', or by en-, zymic hydrolysis'. However, all of these methods usually cause deacylation in the fructosyl moiety. Here we report that octa-0-acetylsucrose (1) was hydrolyzed by lipase OF (Can&a cylindrucea); it was found that deacylation occurred only in the glucosyl moiety of 1.
The hydrolysis of octa-0-acetylsucrose (1) with lipase OF was carefully studied. The major products at different reaction times were isolated. Their structures were analyzed and the pathway of hydrolysis of 1 by lipase OF was proposed in Scheme 1. In our previous reports", it was shown that lipase OF preferentially cleaved the h-acetate to form 2,3,4,1',3',4',6'-hepta-0-acetylsucrose (2) which rearranged nonenzymically to 2,3,6,1',3',4',6'-hepta-0-acetylsucrose (3) through 4 -+ 6 acyl migration'. We now find that the enzyme again attacks the 6-acetate group of 3 to produce 2,3,1',3',4',6'-hexa-0-acetylsucrose (4). A small amount of 2,6,1',3',4',6'hexa-0-acetylsucrose (5) accompanying 4 was found by analysis of NMR spectra and was isolated by HPLC. Since 4 is stable for 120 h in the phosphate buffer, without any acetyl migration, it is believed that 5 is formed by the direct deacylation of the 3-acetate of 3 and not from 4 by 3 + 6 acetyl migration. Finally, the major pentaacetate, 2,1',3',4',6'-penta-0-acetylsucrose (61, was obtained by deacy-