Summary of D-glucofuranose question
Dear CCLers,
I have had a number of useful responses to my question on the existence
of D-glucofuranose and associated energetic considerations. These are
summarized below, with a bit of editorial comment included in brackets ([]).
I hope some find this of use and of interest. -Shaun
ORIGINAL QUESTION...
...Perhaps someone 'in the know' would be kind
enough to enlighten me. That is, D-glucopyranose is always represented to
be the most stable form of glucose (dextrose). However, what about D-
glucofuranose? I've done some crude Hudson-type calculations, but was
never able to convince myself that the furanose form was not unstable and
that it should exist, probably; but, I've never seen it described. What's
the real story? Enlightenment appreciated.
SUMMARY...
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ITEM 1: From: caldwell # - at - # utdallas.edu (Richard A. Caldwell) 1/20/93
Suttie, "Introduction to Biochemistry," Holt, Rinehart, and Winston,
New York, 1972, p 24, says:
The ... furanose ring form of glucose is a less stable form and only a very
small amount is present in the equilibrium mixture. There are, however,
appreciable amounts of the furanose form present in the equilibrium solution
of galactose and some of the rarer hexoses.
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ITEM 2: From: mes # - at - # atlas.chemistry.uakron.edu (Mary Ellen Scott)
1/20/93
I'm not in the know, but I work with sugars. I have seen proton and
carbon 13 NMR data that give ratios of pyranose, furanose, cyclic and I
think hydrated forms of aldo and keto sugars. Are you determining stability
by heat of formation? I have done Mopac calculations on alpha/beta glucose
pyranose form but not furanose. What I would like to determine is the
amount of acyclic form of fluorinated glucose derivatives vs glucose.
If you have any suggestions please email.
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ITEM 3: From: toni # - at - # athe.wustl.edu (Toni Kazic) 1/20/93
...what is a Hudson calculation? ... [Some simple 'wysiwyg' rules to semi-
quantitatively assess the stability of sugar conformers . E.g., axial -OH gets
1 'demerit', axial -CH2OH gets 2 demerits, axial -CH2OH and axial C-1 or 3 OH
get 2.5 demerits, and 3 clustered O torsionally along C1,2 gets 2.5 demerits;
in addition to the classical 'most positive optical rotation is the alpha
anomer'.]
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ITEM 4: From: rwoods # - at - # biop.ox.ac.uk (Bob Woods) 1/21/93
A quick check in "Carbohydrate Chemistry. Monosaccharides and their
Oligomers"
by H.S.El Khadem, Academic Press, 1988 shows:
Composition of Aqueous Solutions of D-Aldoses at Equilibrium
------------------------------------------------------------
Aldose total % pyranose total % furanose
------------ ---------------------- ----------------------
Allose 87 8.5
Altrose 67 33.0
Glucose 100 <0.3
Mannose 100 0.0
Gulose 78 22.0
Idose 75 25.0
Galactose 93 7.0
Talose 69 31.0
Ribose 80 20.0
Arabinose 97 4.5
Xylose 99.5 <0.5
Lyxose 98.0 2.0
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I think you have raised a very interesting question; however, I am not
aware of a suitable explanation of the variations.
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ITEM 5: From: nauss # - at - # wrair-emh1.army.mil (Jeff Nauss) 1/21/93
As an addendum to Shaun Black's request for information about glucofuranose, I
have a small project on-going concerning a molecular dynamics simulation of
galactofuranose. I would also be interested in experiences others have had
with modeling carbohydrates and especially furanose forms.
I have quite a bit already on ribose and deoxyribose but virtually nothing
on any other furanose.
Any suggestions on useful carbohydrate-oriented force fields?
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ITEM 6: From: WTWINTER # - at - # SUVM.acs.SYR.EDU (Bill Winter) 1/21/93
I believe that Adam Allerhand from Univ Indiana published NMR results in the
1970's confirming the coexistence of a small percentage of glucofuranose in the
equilibrium mixture in D2O.
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= Shaun D. Black, PhD | Internet: shaun%jason.decnet # - at - #
relay.the.net =
= Dept. of Biochemistry | Bitnet: shaun%jason.decnet # - at - #
thenic.bitnet =
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