Abstract Seven-membered cyclic sugars are known as septanoses and septanosides. Whereas furanose and pyranose structures represent the known naturally available sugars, the seven-membered septanose sugars are confined to be only in the... more
Abstract Seven-membered cyclic sugars are known as septanoses and septanosides. Whereas furanose and pyranose structures represent the known naturally available sugars, the seven-membered septanose sugars are confined to be only in the synthetic regime as yet. Synthetic explorations and structural studies contribute immensely to bring out many facets of septanoses in recent years. Innovative synthetic strategies drive advancements in septanose sugars. Cyclization of acyclic precursors, ring expansions, and rearrangements of existing scaffolds are major approaches to synthesize septanosides. Studies in the furanose and pyranose and solution phase provide finer details of hither-to unknown structural features, aiding further the desire to uncover newer possibilities of this unnatural sugar structures. Following a brief historical overview, this chapter presents a succinct compilation of the progress in synthetic and structural studies of this class of sugars.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT The guaianolide ring containing sesquiterpene thapsigargin is found in the roots and fruits of Mediterranean plant Thapsia garganica L. It is known for its activity as a potent antagonist for Ca2+-ATPase (sarco–endoplasmic... more
ABSTRACT The guaianolide ring containing sesquiterpene thapsigargin is found in the roots and fruits of Mediterranean plant Thapsia garganica L. It is known for its activity as a potent antagonist for Ca2+-ATPase (sarco–endoplasmic reticulum Ca2+-ATPase) inhibition. Recently, a prodrug mipsagargin is being investigated to target the blood vessel of the cancer cells for the treatment of tumors. The limited natural supply (low isolation and only localized growth (Mediterranean area)) from the natural sources strongly urges for the development of chemical synthetic strategies to access these natural products. This review pertain the various strategies used so far in the thapsigargin’s synthesis, focusing on major contributions in the total synthesis till date. GRAPHICAL ABSTRACT
Research Interests:
Research Interests:
The solid state structure of a new seven-membered sugar oxepane derivative, namely, p-bromo phenyl 4,5,7-tri-O-benzyl-β-d-glycero-d-talo-septanoside is discussed, as determined through single crystal X-ray structural determination and in... more
The solid state structure of a new seven-membered sugar oxepane derivative, namely, p-bromo phenyl 4,5,7-tri-O-benzyl-β-d-glycero-d-talo-septanoside is discussed, as determined through single crystal X-ray structural determination and in relation to their conformational features. The molecule adopts twist-chair as the preferred conformation, with conformational descriptor (O,1)TC2,3. The solid state packing of molecules is governed by a rich network of non-covalent bonding originating from O-H⋯O, C-H⋯π, C-H⋯Br and aromatic π⋯π interactions that stabilize the packing of molecules in the crystal.
Research Interests:
Single crystal X-ray structural analysis of a septanoside, namely, n-pentyl-2-chloro-2-deoxy sept-3-uloside (1) provides many finer details of the molecular structure, in addition to its preferred twist-chair conformation, namely,... more
Single crystal X-ray structural analysis of a septanoside, namely, n-pentyl-2-chloro-2-deoxy sept-3-uloside (1) provides many finer details of the molecular structure, in addition to its preferred twist-chair conformation, namely, (5,6)TC3,4 conformation. Structural analysis reveals a dense network of O-H⋯O, C-H⋯O and van der Waals interactions that stabilize interdigitized, planar bi-layer structure of the crystal lattice.
Research Interests:
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... more
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 monosaccharide. Further the glycosidic bond at the reducing end hydrolyzes almost twice as 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.
Research Interests:
This paper deals with the synthesis of 2-deoxy-2-C-alkyl/aryl septanosides. A range of such septanoside derivatives was synthesized by using a common bromo-oxepine intermediate, involving C–C bond forming organometallic reactions.... more
This paper deals with the synthesis of 2-deoxy-2-C-alkyl/aryl septanosides. A range of such septanoside derivatives was synthesized by using a common bromo-oxepine intermediate, involving C–C bond forming organometallic reactions. Unsaturated, seven-membered septanoside vinyl bromides or bromo-oxepines, obtained through a ring expansion methodology of the cyclopropane derivatives of oxyglycals, displayed a good reactivity towards several acceptor moieties in C–C bond forming Heck, Suzuki and Sonogashira coupling reactions, thus affording 2-deoxy-2-C-alkyl/aryl septanosides. Whereas Heck and Sonogashira coupling reactions afforded 2-deoxy-2-C-alkenyl and -alkynyl derivatives, respectively, the Suzuki reaction afforded 2-deoxy-2-C-aryl septanosides. Deprotection and reduction of the 2-deoxy-2-alkenyl derivative afforded the corresponding 2-deoxy-2-C-alkyl septanoside free of protecting groups. The present study illustrates the reactivity of bromo-oxepine in the synthesis of hitherto u...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Conformational analysis of unnatural seven-membered sugars, namely, septanoses and septanosides are discussed herein. The conformational properties of these sugars in the solid state, solution phase and computational methods are... more
Conformational analysis of unnatural seven-membered sugars, namely, septanoses and septanosides are discussed herein. The conformational properties of these sugars in the solid state, solution phase and computational methods are presented. The analyses reveal that conformations of septanosides are diverse and largely unpredictable, as compared furanosides and pyranosides.
Research Interests:
We report the design of building blocks with optimized reactivities for the programmable one-pot synthesis of heparin pentasaccharides with regiodefined sulfation patterns.