85 ニトロベンジル基およびピバロイルアミノベンジル基による水酸基の保護とその糖質合成への応用(口頭発表の部)

概要

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Novel application was studied of 4-nitrobenzyl (4-nitrophenyl-methyl, NPM) and 4-pivaloylaminobenzyl (4-pivaloylaminophenyl-methyl, PPM) groups to the protection of hydroxyl functions in the synthesis of complex carbohydrates. NPM ether formed with NPM bromide and Ag_2O is stable under acidic and various other conditions employed for the cleavage of many of common protecting groups. After reductive conversion, however, the resulting 4-aminobenzyl group could be highly selectively removed by mild anodic oxidation. Mild chemical reduction of the nitro group with Zn powder and acetylacetone enabled the selective cleavage of NPM group even in the presence of a double bond in the molecule. DDQ oxidation also proved to be effective for the cleavage of aminobenzyl function particularly after N-acylation. Thus PPM ether which could be formed either via reduction of NPM and N-acylation or directly by the acid-catalyzed reaction of the corresponding imidate has a high practical value for temporary protection of hydroxyl groups in multistep synthesis. NPM groups was then successfully employed in the synthesis of a trisaccharide, α-D-Xylp(1-3)-α-D-Xylp(1-3)-β-D-Glcp, and its conjugate with L-Ser which was recently isolated and characterized from blood clotting factor protein. Selective cleavage of NPM as well as PPM was also utilized effectively in the synthesis of the glycolipid part of bacterial lipoteichoic acid.
1990-09-25