Stereoselective synthesis of a C-glycosylic compound (a "methyl C-glycoside") through a regioselective free-radical ring-opening reaction. A single-crystal X-ray structure determination.
TL;DR: Cyclopropanation of 4,6-O-benzylidene-D-glucal, followed by tributylstannyl radical-mediated regioselective ring opening of the 1,2-cyclopropano sugar led to a 2, 6-anhydro-1-deoxyheptose, (a "methyl C-beta- D-glycoside").
About: This article is published in Carbohydrate Research.The article was published on 2002-09-27. It has received 3 citations till now. The article focuses on the topics: Glucal.
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TL;DR: The osmium-catalyzed aminohydroxylation of glycals has been achieved with complete regio- and stereocontrol by taking advantage of the Donohoe tethering approach.
11 citations
TL;DR: Kalpattu Kuppuswamy Balsubramanian (popularly and affectionately addressed as KKB) was born on September 5th 1939, at Mylapore, Madras (now Chennai), Tamil Nadu, India, in a family gifted with tradition in the noble profession of teaching.
Abstract: Kalpattu Kuppuswamy Balsubramanian (popularly and affectionately addressed as KKB) was born on September 5th 1939, at Mylapore, Madras (now Chennai), Tamil Nadu, India, in a family gifted with tradition in the noble profession of teaching.[...]
2 citations
TL;DR: In the title compound, C21H22Cl2O4, the pyranosyl ring adopts a twist-boat conformation with the O-benzyl groups in equatorial positions, which results in infinite chains of molecules along the crystal.
Abstract: In the title compound, C(21)H(22)Cl(2)O(4), the pyranosyl ring adopts a twist-boat conformation with the O-benzyl groups in equatorial positions. In the crystal, O-H⋯O hydrogen bonding results in infinite chains of mol-ecules along [100]. The structure is further consolidated by weak C-H⋯O, C-H⋯Cl and C-H⋯π inter-actions. The absolute structure was determined.
Cites methods from "Stereoselective synthesis of a C-gl..."
...For a related structure, see: Shanmugasundaram et al. (2002)....
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...Although 1H NMR data could be used to establish the structure of the product, the highly reactive and strained bicyclic junction requires single-crystal X-ray diffraction study to determine the stereochemistry of the product (Shanmugasundaram et al., 2002) In the title compound (Fig....
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TL;DR: In this article, a phase annealing method, related to the simulated-annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution.
Abstract: A number of extensions to the multisolution approach to the crystallographic phase problem are discussed in which the negative quartet relations play an important role. A phase annealing method, related to the simulated annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution. The ideas presented here are incorporated in the program system SHELX-90; the philosophical and mathematical background to the direct-methods part (SHELXS) of this system is described.
14,787 citations
324 citations
TL;DR: In this article, a short review on the biosynthesis of deoxy oligosaccharides is presented, and the general techniques including classical methods as well as recent stereospecific procedures for deoxy glycosides are outlined.
Abstract: This paper focusses on stereoselective syntheses of deoxy oligosaccharides which are an integral part of a number of antibiotics and cytostatics. Following a short review on the biosynthesis of these sugars, the general techniques including classical methods as well as recent stereospecific procedures for the preparation of deoxy glycosides are outlined.
95 citations
TL;DR: In this article, a cyclopropanation of glycals 1, 2, 3, 4, and 41 was carried out using either dihalocarbene addition or zinc-carbenoid addition to yield 1,2-cyclopropanated sugars.
Abstract: Diastereospecific cyclopropanation of glycals 1, 2, 3, 4, and 41 was carried out using either dihalocarbene addition or zinc-carbenoid addition to yield 1,2-cyclopropanated sugars. Dichloro- and dibromocarbenes added stereoselectively anti to the C3 benzyloxy group, whereas (under Simmons−Smith conditions) the cyclopropanes were formed syn to the same substituent. The reactions of these 1,2-cyclopropanated sugars to provide either ring expanded glycosides or C2-branched chain glycosides were explored. Solvolytic ring expansion of 1,2-dibromocyclopropanated sugars with K2CO3 in refluxing methanol yielded the corresponding chiral oxepins 20−22. Electrophilic ring openings of parent cyclopropanes (14 and 17 derived from glucal 1) were carried out with different electrophiles to give functionalized 2-deoxy-2-C-branched chain glycosides. The ring openings of 14 in different solvents resulted in both α- and β-anomers, whereas 17 gave exclusively the α-anomer.
89 citations
TL;DR: A review of the formation and chemistry of cyclopropanated carbohydrates can be found in this paper, where the authors provide a synopsis of the cycloprocessed carbohydrate synthesis process.
Abstract: This review provides a synopsis of the formation and chemistry
of cyclopropanated carbohydrates. The organization begins with methods for
the formation of the cyclopropanated carbohydrate followed by the chemistry
of the bicyclic system. Examples of new reactions and rearrangements
leading to new products and the synthesis of natural products are
presented.
89 citations