|Budget Amount *help
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1993 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1992 : ¥1,300,000 (Direct Cost : ¥1,300,000)
The objective of this study is to synthesize well-defined branched(1-3)-beta-D-glucans having beta-D-glucoss branches at their 6-positions via ring-opening polymerization of 1,3-anhydro sugar derivatives. Synthesis of the target polysaccharides was undertaken by two different approaches : 1)Polymerization of 1,3-anhydro-beta-D-glucose derivative (1), followed by selective deprotection of the p-methoxybenzyl group of the resulting polymer, subsequent stereospecific glycosidation at the 6-position, and finally complete deprotection of the product, and 2) polymerization of 1,3-anhydro-beta-D-glucose derivative (2) bearing a beta-D-glucose moiety in its 6-position, followed by deprotection of the resulting polymer.
The synthesis of 1 was attempted via a 9 steps reaction sequence starting from cellulose. However, the methoxybenzyl group was removed during the chlorination of the diacetate (3) by hydrogen chloride. Therefore it is necessary to look for a more appropriate protecting group as well as milder reaction conditions. The synthesis of 2 was also undertaken with cellulose as a starting material through an 11 step reaction sequence. In the final intermolecular bicyclization step, the dehydrochlorination of the precursor chloride (4) predominantly occurred to yield a glucal derivative as the major product. The monomer 2 was cbtained in a yield of 14%. Therefor, the reaction conditions must be optimized to improve the yield of the desired product 2.
Polymerization of 1,3-anhydro-2,4,6-tri-O-benzyl-beta-D-glucopyranose was investigated in order to clarify the factors influencing the stereospecific polymerization of 1,3-anhydro sugar derivatives by modified organoaluminum catalysts.