REGIOSELECTIVITY OF ALKYLATION OF CYCLOMALTOHEPTAOSE (BETA-CYCLODEXTRIN) AND SYNTHESIS OF ITS MONO-2-O-METHYL, MONO-2-O-ETHYL, MONO-2-O-ALLYL, AND MONO-2-O-PROPYL DERIVATIVES

Mono-2-O-methyl-, -2-O-ethyl-, and -2-O-allyl-cyclomaltoheptaose were prepared by alkylations of cyclomaltoheptaose in dilute aqueous alkali , and mono-2-O-propylcyclomaltoheptaose was obtained by hydrogenation of the allyl derivative. Ah the 2-O-alkyl derivatives were less solubl e in water than was cyclomaltoheptaose. All formed inclusion complexes with toluene in aqueous solution, but only the methyl ether was less soluble in the water-toluene system than in water. The solubilities of the other ethers in water were enhanced by the addition of toluene. P artial methylation of cyclomaltoheptaose with C-13-enriched dimethyl s ulfate in dilute aqueous alkali yielded mixtures of products. The subs titution patterns were analyzed by GLC-MS of the alditol acetates, pre pared by hydrolysis, reduction, and acetylation, and by C-13 NMR after complete permethylation with nonenriched reagent. The results showed that methylation at O-2 is a predominant but not an exclusive reaction ; as expected, the regioselectivity decreases with increasing degree o f methylation.