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Synthesis and Molecular Geometry of an Achiral 30‐Crown‐12 Polyacetal from α ‐Cyclodextrin
Author(s) -
Immel Stefan,
Nakagawa Toshio,
Lindner Hans J.,
Lichtenthaler Frieder W.
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20000915)6:18<3366::aid-chem3366>3.0.co;2-9
Subject(s) - hydroxymethyl , chemistry , crystallography , glycolaldehyde , borohydride , cyclodextrin , stereochemistry , crystallization , catalysis , organic chemistry
Periodate oxidation of α ‐cyclodextrin followed by borohydride reduction readily provided an octadeca‐Hydroxymethyl‐substituted 30‐crown‐12 polyacetal 1 , its 30‐membered macrocycle being composed of six meso ‐butanetetrol/glycolaldehyde acetal units, which is, consequently, optically inactive. Its solid‐state molecular geometry emerged from the X‐ray structural analysis of the well‐crystallizing octadecaacetate 2 , which revealed the undulated macrocycle to be molded into three loops with a unique order of succession of the ‐CHRCHROCHRO‐ units: alternating gauche‐ and anti ‐conformations of the meso ‐butanetetrol portions and consecutive disposition of the glycolaldehyde‐acetoxymethyl groups above and below the mean‐plane of the macrocycle. In solution, however, as evidenced by 1 H‐ and 13 C‐NMR spectra, the macrocycle is highly flexible at ambient and higher temperatures, its mobility becoming distinctly restricted only below −20 °C.