INTERGLYCOSIDIC ACETALS .3. SYNTHESIS AND STRUCTURE DETERMINATION OF CYCLIC MONOBENZYLIDENE ACETALS OF CYCLODEXTRIN DERIVATIVES BRIDGING BETWEEN TWO CONTIGUOUS D-GLUCOPYRANOSYL RESIDUES

摘要

Transacetalation of fully 6-O-pivaloylated alpha-, beta-, and gamma-cyclodextrins with benzaldehyde dimethylacetal in the presence of (+)-10-camphorsulfonic acid gave monobenzylidene acetals (4, 5, 6) in moderately good yields. Benzylation of the beta-cyclodextrin derivative 5 followed by acid-catalyzed hydrolysis of the benzylidene group and acetylation afforded a di-O-acetyl-nonadeca-O-benzyl derivative 9. NMR spectroscopic analysis of 9, including two-dimensional HOHAHA and H-1-C-13 correlation experiments revealed that the benzylidene group bridged the O-2 and O-3 positions of contiguous D-glucopyranosyl residues. Reductive ring-opening of the benzylidene acetal with lithium aluminum hydride/aluminum chloride afforded predominantly a 2(1)-O-unprotected derivative 10 in good yield. (C) 1996 Elsevier Science Ltd. [References: 12]