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Regioselective Hydrolyses of Partially pivaloylated Mannose Derivatives Catalysed by Esterases from Mammalian Sera

It has been previously shown that O-acyl derivatives of mannose are good substrates in hydrolyses reactions catalyzed by enzymes. Regioselective deacylations occur, and the direction of regioselectivity depends on reaction conditions and the enzyme source1. Migrations of acetyls1 and less frequent pivaloyls were also noticed3. In this work we present the synthesis of methyl 3, 6-di-O-pivaloyl-alpha-D-mannopyranoside (1), its transformation to methyl 2, 6-di-O-pivaloyl-alpha-D-mannopyranoside (2) by intramolecular migration of the 3-pivaloyl group caused by the reaction medium (buffered solution, pH=7.2, 60C). The mechanism of this reaction is also discussed4. Furthermore, comparative study was done on regioselective deacylations of methyl 2, 6-di-O-pivaloyl-alpha-D-mannopyranoside (2) catalysed by esterases from rabbit and guinea pig sera. 1. Đ. Ljevaković, D. Parat, J. Tomašić, S. Tomić, Croat. Chem. Acta 68 (1995) 477-484. 2. S. Tomić, Đ. Ljevaković, J. Tomašić, Tetrahedron 49 (1993) 10977-10986. 3. S. Tomić, Lj. Sesartić, J. Tomašić, Comp. Biochem. Physiol. 92 B (1989) 681-684. 4. T. Horrobin, Ch. H. Tran, D. Crout, J. Chem. Perkin Tans I (1998) 1069-1080.

regioselective hydrolyses; mannose derivatives; mammalian sera

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