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Large Ring Crown Acetals from Cyclodextrins

Toshio Nakagawa, Stefan Immel, Hans Jörg Lindner, and F. W. Lichtenthaler

XVIIth Japanese Cyclodextrin Symposium, Osaka, Japan, October 13-14, 1999.

Periodate oxidation of α- to γ-cyclodextrins followed by borohydride reduction gave the 30-, 35-, 40-membered cyclic crown acetals, which were isolated and characterized in the form of their achiral crystalline per-O-acetates. An X-ray analysis of the α-CD derived crown acetal revealed a unique topology: three acetoxyethylidene units are located inside the macro-ring, and the other three outside; of the six diacetoxy-meso-butane units, three are in a gauche and the other three in a trans arrangement.

Synthesis of crown acetals from cyclodextrins

30-membered crown acetal
Solid-state conformation
Fig. 1: Conformation of Iα in the crystal with one meso-butanetetrol gauche- and trans-conformation labeled (cf. formula on the left; all acetyl groups and hydrogen atoms omitted for clarity).

[1] L. Kandra, A. Liptak, A. I. Jodal, P. Nanasi, J. Szejtli, J. Inclusion Phenom. 1984, 2, 869-875.

Additional Graphics: Crown Acetals

© Copyright PD Dr. S. Immel