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Studies on ketoses, 10 . Acylation and carbamoylation of D ‐fructose: Acyclic, furanoid and pyranoid derivatives and their conformational features
Author(s) -
Lichtenthaler Frieder W.,
Klotz Jürgen,
Flath FranzJosef
Publication year - 1995
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.1995199512292
Subject(s) - chemistry , acylation , stereochemistry , enantiopure drug , tautomer , anomer , furanose , pyridine , ring (chemistry) , organic chemistry , enantioselective synthesis , catalysis
Acylations of D‐fructose are complicated at several levels. The product distribution is determined not only by the rate of equilibration of the crystalline β‐ p ‐form in pyridine to the α‐ p , β‐ f , and α‐ f ‐tautomers, but also by the distribution of these forms at a given temperature, as well as their individual hydroxyl group. A detailed study of these parameters resulted in the elaboration of new or improved procedures for the practical, straightforward preparation of either acyclic, furanoid, or pyranoid benzoyl and pivaloyl derivatives, as well as cyclocarbamates with 1,2‐ spiro ‐annelated and 2,3‐bridging oxazolidinone rings. Accordingly, a variety of simple, tautomerically fixed fructose derivatives, most notably those of the α‐ p , α‐ f and β‐ f forms, are now easily accessible for exploitation as versatile enantiopure building blocks. The structures, anomeric configurations and conformations of the various products obtained were determined on the basis of their 1 H and 13 C NMR data. The furanoid cases required the support of two X‐ray structures: the pentabenzoyl‐α‐ D ‐fructofuranose ( 9 ) which has an E 2 conformation, and the 2,3‐cyclocarbamate 25 , in which the β‐furanose ring adopts a 5 E geometry.