Synthesis and monolayer behavior of amphiphilic per(2,3-di-O-alkyl)-alpha-and beta-cyclodextrins and hexakis(6-deoxy-6-thio-2,3-di-O-pentyl)-alpha-cyclodextrin at an air-water interface

A synthesis of amphiphilic per(2,3-di-O-alkyl)-alpha- and beta -cyclodextri ns and hexakis(6-deoxy-6-thio-2,3-di-O-pentyl)-alpha -cyclodextrin and thei r monolayer behavior on a water surface is presented. Long alkyl chains wer e introduced by a treatment of the per(6-O-tert-butyldimethylsilyl) derivat ives with an appropriate alkyl iodide in dimethylformamide in the presence of sodium hydride. A standard desilylation procedure followed by an iodinat ion reaction afforded per(6-deoxy-6-iodo) analogues. In the latter reaction step, sulphur containing groups were introduced by nucleophilic substituti on of the iodine with benzothiolate ion in dimethylformamide. The hexakis(6 -deoxy-6-S-benzyl-2,3-di-O-pentyl)-alpha-cyclodextrin was transformed into extremely interesting hexakis(6-deoxy-6-thio-2, 3-di-O-pentyl)-alpha -cyclo dextrin. The surface pressure-mean molecular area (pi -A) isotherms indicat ed that the synthesised amphiphilic cyclodextrin derivatives were capable o f forming stable monolayers at the air-water interface. The shapes of the i sotherms were typical for solid-like monolayers except for hexakis(6-deoxy- 6-thio-2,3-di-O-pentyl)cyclomaltohexaoses which formed a more liquid monola yer. (C) 2000 Elsevier Science Ltd. All rights reserved.