Glycosidic bond hydrolysis in septanosides: A comparison of mono-, di-, and 2-chloro-2-deoxy-septanosides

Article abstract of DOI:10.1016/j.carres.2014.05.013

A kinetic study of the hydrolytic stabilities of mono-, di-, and 2-chloro-2-deoxy septanosides, under acid-catalysis, is reported herein. A comparison of mono- and diseptanosides, shows that the glycosidic bond in the disaccharide is more stable than the

Full text of DOI:10.1016/j.carres.2014.05.013

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Accepted Manuscript
Glycosidic Bond Hydrolysis in Septanosides: A Comparison of Mono-, Di- and
2-Chloro-2-Deoxy-Septanosides
Supriya Dey, N. Jayaraman
PII:
S0008-6215(14)00205-5
DOI:
http://dx.doi.org/10.1016/j.carres.2014.05.013
CAR 6752
Reference:
Carbohydrate Research
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Received Date:
Revised Date:
Accepted Date:
15 April 2014
14 May 2014
17 May 2014
Please cite this article as: Dey, S., Jayaraman, N., Glycosidic Bond Hydrolysis in Septanosides: A Comparison of
Mono-, Di- and 2-Chloro-2-Deoxy-Septanosides, Carbohydrate Research (2014), doi: http://dx.doi.org/10.1016/
j.carres.2014.05.013
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Glycosidic Bond Hydrolysis in Septanosides: A Comparison of Mono-, Di-
and 2-Chloro-2-Deoxy-Septanosides
Supriya Dey and N. Jayaraman*
Department of Organic Chemistry, Indian Institute of Science, Bangalore-560012, India
Phone: +91-80-2293-2578; Fax: +91-80-2360-0529
Phone: +91-80-2293-2578; Fax: +91-80-2360-0529
E-mail: jayaraman@orgchem.iisc.ernet.in
Graphical abstract for table of contents
1

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Glycosidic Bond Hydrolysis in Septanosides: A Comparison of Mono-, Di-
and 2-Chloro-2-Deoxy-Septanosides
Supriya Dey and N. Jayaraman*
Department of Organic Chemistry, Indian Institute of Science, Bangalore-560012, India
Phone: +91-80-2293-2578; Fax: +91-80-2360-0529
Phone: +91-80-2293-2578; Fax: +91-80-2360-0529
E-mail: jayaraman@orgchem.iisc.ernet.in
Abstract-A kinetic study of the hydrolytic stabilities of mono-, di- and 2-chloro-2-deoxy
septanosides, under an acid-catalysis, is reported herein. A comparison of mono-and
diseptanosides, shows that glycosidic bond in the disaccharide is more stable than the
monosaccharide. Further the glycosidic bond at the reducing end hydrolyzes almost twice
faster than that of the non-reducing end of the disaccharide. 2-Chloro-2-deoxy septanoside is
found to be the most stable and its glycosidic bond hydrolysis occurs at elevated temperatures
only. The orientation of the exo-cyclic hydroxymethyl group and the inductive effect are
suggested to play a role in the rates of hydrolysis.
Keywords: Carbohydrates; Glycosidic bond; Hydrolysis; Kinetics; Septanosides
2

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1. Introduction
Hydrolytic stabilities of glycosidic bonds play a major role in manifold chemical and
biological functions of sugars.1,2 Differences in the rates of hydrolysis of anomeric and
epimeric furanosides and pyranosides were studied in detail.3-9 Factors, such as, steric
interactions, field and electronic effects control the rate of hydrolysis.10-12 On the other hand,
the hydrolytic stabilities of glycosidic bond in seven-membered ring sugars, namely,
septanoside are not known in great detail currently. Peczuh and co-workers showed that the
rate of hydrolysis of methyl-α-septanoside was much faster than pyranoside analogues, under
an acid-catalyzed condition,13, 14 as a result of structural flexibility of the seven-membered
ring systems. It was observed that α-anomer hydrolysed 2 times faster than the β-anomer,
which contradicted the results in case of α/β-pyranosides. The hydrolytic stabilities of seven
carbons analogues of pyranosides, namely, 4-C-hydroxymethyl-linked mono- and
disaccharides were studied by us previously.15 An outcome of the study was that the
glycosidic bond of such hepto-pyranosides was more stable at the reducing end than the non-
reducing end of disaccharide, in comparison to the corresponding pyranoside disaccharides.
In continuation of an interest on hydrolytic stabilities, we undertook acid-catalyzed
hydrolysis of the glycosidic bond in septanosides. The study herein focuses on three closely-
related septanosides, namely, n-pentyl septanoside, α-1,7-linked diseptanoside and 2-chloro-
2-deoxy septanoside.
2. Results and discussion
Synthesis of n-pentyl α-D-glycero-D-galacto-septanoside: Synthesis of n-pentyl septanoside
was initiated from a hydroxyl glycal ether, or an oxyglycal.16 A cyclopropanation of
oxyglycal I was performed using in situ generated dichlorocarbene. The carbene addition
afforded 2, as a single diastereomer, in a good yield. Reaction of n-pentanol with 1, using
3