Can I read Organofluorine compounds and fluorinating agents, 10. Unusual regio- and stereoselective 3,4-acetalizations of selected pyranosides by hexafluoroacetone as a result of a new reaction pathway on EtoBox?

Organofluorine compounds and fluorinating agents, 10. Unusual regio- and stereoselective 3,4-acetalizations of selected pyranosides by hexafluoroacetone as a result of a new reaction pathway by Ralf Miethchen; Daniel Rentsch; Manfred Michalik is a Chemistry article available to read on EtoBox.

What is Organofluorine compounds and fluorinating agents, 10. Unusual regio- and stereoselective 3,4-acetalizations of selected pyranosides by hexafluoroacetone as a result of a new reaction pathway about?

## Abstract Regio‐ and stereoselective direct acetalizations of chiral vicinal polyols with hexafluoroacetone (HFA) are described. Thus, the reaction of methyl α‐D‐mannopyranoside (1) and methyl a‐L‐rhamnopyranoside (5) with HFA affords cyclic 3, 4‐Acetals accompanied by simultaneous inversion of configuration at C‐3 when __N, N__′‐dicyclohexylcarbodiimide (DCC) is added as a coreagent. Methyl 2‐O‐(cyclohexylcarbamoyl)‐3, 4‐O‐(hexafluoroisopropylidene)‐a‐D‐altropyranoside (2) and methyl 6‐deoxy‐3, 4‐O‐(hexafluoroisopropylidene)‐a‐L‐altropyranoside (6), respectively, have been found to be the major products. The carbamoyl groups found in 2 and moreover in the byproduct 7 may be cleaved by methanolysis giving the Acetals 3 and 6, respectively. All of the products, 2, 3, 6, and 7 adopt a boat conformation as confirmed by NMR data and, additionally, ensured by X‐ray analysis in the case of 7. The incorrect structural formula for compound 6, reported as “methyl 2, 3‐O‐(hexafluoroisopropylidene)‐ct‐L‐rhamnopyranoside” in ref. [2], has to be corrected. The direct Acetalization described in this paper probably includes an intramolecular nucleophilic attack of a hemiacetal oxygen (4‐positio

Who reads Organofluorine compounds and fluorinating agents, 10. Unusual regio- and stereoselective 3,4-acetalizations of selected pyranosides by hexafluoroacetone as a result of a new reaction pathway?

Author

Ralf Miethchen; Daniel Rentsch; Manfred Michalik

Publisher

John Wiley and Sons; Wiley (John Wiley & Sons); VCH Verlagsgesellschaft; Wiley (ISSN 0947-3440)

Published

1994

Language

EN

Field

Chemistry (Physical Sciences)