Synthesis of per(5-carboxy-5-dehydroxymethyl)-alpha-cyclodextrin and beta-cyclodextrin - self-assembly of the per(2,3-di-O-methyl)-protected homologues into highly stable dimers, driven by multiple hydrogen bonds

Per(2,3-di-O-methyl)- and per(2,3-di-O-acetyl)- alpha- and beta-cyclodextri ns were smoothly converted into the corresponding per(5-carboxy-5-dehydroxy methyl) derivatives 2a, 2b, 4a and 4b by TEMPO-mediated oxidation. Alkaline hydrolysis of the per(2,3-di-O-acetyl) -substituted polycarboxylic acids a ffords the naked per(5-carboxy-5-dehydroxymethyl) cyclodextrins 5a and 5b i n quantitative yields. Self-assembly, driven by hydrogen bonds, of the per( 2,3-di-O-methyl)-protected homologues 2a and 2b affords highly stable dimer s, as evidenced by vapour-pressure osmometry in 1,2-dichloroethane solution .