Isolation and characterisation of an unexpected byproduct in the regioselective butane diacetal protection of α-methyl galactopyranoside
Isolation and characterisation of an unexpected byproduct in the regioselective butane diacetal protection of α-methyl galactopyranoside
The regioselective protection of both methyl galactopyranoside anomers at the 2 and 3-positions as the butane diacetal (BDA) is well known. Here we describe the formation of an unexpected byproduct, which mainly occurs when α-methyl galactopyranoside is reacted with 2,3-butanedione under BF3•OEt2 catalysis. The structure of the byproduct, which did not arise from anomerisation to the β-anomer or from BDA formation at the galactopyranoside 3,4-positions, was elucidated by NMR and X-ray crystallographic analysis, and proved to be the expected BDA protected galactopyranoside, but in which the stereochemistry of both its BDA acetal centres are inverted. Interestingly, the conformation of the resulting six-membered BDA ring was distorted to a skew boat conformation in order to maintain anomeric stabilisation.
Galactose, Butane diacetal, regioselective, Conformation
14-17
Fontenelle, Clement Q.
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Kuppala, Ramakrishna
c92bd85a-9009-4d33-99ca-a9ee3b457d44
Light, Mark
cf57314e-6856-491b-a8d2-2dffc452e161
Linclau, Bruno
19b9cacd-b8e8-4c65-af36-6352cade84ba
2 January 2018
Fontenelle, Clement Q.
929410b0-7dcb-4c83-a9f7-ef2be8e81fbb
Kuppala, Ramakrishna
c92bd85a-9009-4d33-99ca-a9ee3b457d44
Light, Mark
cf57314e-6856-491b-a8d2-2dffc452e161
Linclau, Bruno
19b9cacd-b8e8-4c65-af36-6352cade84ba
Fontenelle, Clement Q., Kuppala, Ramakrishna, Light, Mark and Linclau, Bruno
(2018)
Isolation and characterisation of an unexpected byproduct in the regioselective butane diacetal protection of α-methyl galactopyranoside.
Carbohydrate Research, 455, .
(doi:10.1016/j.carres.2017.10.023).
Abstract
The regioselective protection of both methyl galactopyranoside anomers at the 2 and 3-positions as the butane diacetal (BDA) is well known. Here we describe the formation of an unexpected byproduct, which mainly occurs when α-methyl galactopyranoside is reacted with 2,3-butanedione under BF3•OEt2 catalysis. The structure of the byproduct, which did not arise from anomerisation to the β-anomer or from BDA formation at the galactopyranoside 3,4-positions, was elucidated by NMR and X-ray crystallographic analysis, and proved to be the expected BDA protected galactopyranoside, but in which the stereochemistry of both its BDA acetal centres are inverted. Interestingly, the conformation of the resulting six-membered BDA ring was distorted to a skew boat conformation in order to maintain anomeric stabilisation.
Text
BDA paper_v11_corrected_headings
- Accepted Manuscript
More information
Accepted/In Press date: 29 October 2017
e-pub ahead of print date: 6 November 2017
Published date: 2 January 2018
Keywords:
Galactose, Butane diacetal, regioselective, Conformation
Identifiers
Local EPrints ID: 415924
URI: http://eprints.soton.ac.uk/id/eprint/415924
ISSN: 0008-6215
PURE UUID: cddbf0f5-27f9-445b-8474-7d0a1ed5defa
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Date deposited: 28 Nov 2017 17:31
Last modified: 16 Mar 2024 05:57
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Contributors
Author:
Clement Q. Fontenelle
Author:
Ramakrishna Kuppala
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