Carbohydrates natural products, syntheses

The regio- and stereo-selective functionalization of aldonolactones yields optically active lactones, which are important precursors in natural product synthesis. Concepts such as chiral templates and chirons, derived from carbohydrates, have been ingeniously and widely applied in synthesis (233). Among the commercially available aldonolactones, D-ribono-1,4-lactone is... 

K. Tadano, Natural product synthesis starting with carbohydrates based on the Claisen rearrangement protocol, in Studies in Natural Products Chemistry, Atta-ur Rahman, ed., Elsevier Science, New York, 1992, pp. 405-455. 

Sugar-Derived Building Blocks for the Synthesis of Non-Carbohydrate Natural Products... 

Carbohydrate synthons in natural product synthesis" which is the title of this special symposium has an inevitable problem to be solved, because we often need both enantiomers of synthons for the synthesis of optically active natural... 

The inverse electron demand hetero Diels-Alder reaction of 1-oxa-l,3-butadienes and electron-rich dienophiles is an extremely versatile tool in natural product synthesis. This cycloaddition represents the key step of numerous approaches not only to carbohydrates, but also to terpenes, alkaloids, polyethers, steroid derivatives and various biologically active metabolites. 

Although several aspects of alkene metathesis need further improvement or remain to be solved, there is no doubt that this transformation has a profound impact on all sub-disciplines of modern organic chemistry and will continue to shape preparative carbohydrate chemistry and natural product synthesis in the future. 

Amino acids, peptides, and proteins Asymmetric synthesis and induction Beta-lactam antibiotics Carbohydrates (chemical aspects) Natural product synthesis New antibiotics... 

The stereochemical outcome of the addition of carbanions to ketones yielding tertiary alcohols (or secondary alcohols in the case of aldehydes) is variable and depends on the substrate, the counterion and the solvent. Numerous applications of this strategy to natural product synthesis from carbohydrates can be found in the literature and this approach was fruitful in pioneering syntheses of polyketide-type products. Here again, the template effect of the sugar plays a tremendous role in the stereochemical outcome of the reaction. Chelation controlled nucleophilic addition can also be used to form chiral centers in a highly predictable way. 

O. Kanie, M. Kiso, and A. Hasegawa, Glycosylation using methylthioglycosides of IV-acetyl-neuraminic acid and dimethyl(methylthio)sulfonium triflate, / Carbohydr. Chem. 7 501 (1988). K. Toshima and K. Tatsuta, Recent progress in 0-glycosylation methods and its application to natural products synthesis, Chem. Rev. 93 1503 (1993). 

The TPAP/NMO system [24] and the Dess-Martin periodinane [31] have been widely applied for oxidizing alcohols in complex natural product synthesis. Although both reagents are commercially available, they have so far found relatively little use in carbohydrate chemistry for oxidation of primary alcohols to aldehydes [44,45]. 

The potential of the ester enolate Claisen rearrangement for the stereocontrolled synthesis of highly functionalized, complex systems has been demonstrated in numerous applications in natural product synthesis. Utilizing the 1,3-chirality transfer Ireland has synthesized oxygen heterocycles with chiral side chains, such as are found as units in polyether antibiotics and macrolides, starting from enantiomerically pure furanoid or pyranoid glycal systems of type (41), which are easily accessible from carbohydrates (Scheme 65). ... 

TIPDSCI2, DMF, imidazole. This reagent is primarily used in carbohydrate protection, but occasionally it proves valuable in other circumstances. Its use in natural product synthesis has been reviewed. ... 

Toshima K (2006) Novel glycosylation methods and their application to natural products synthesis. Carbohydr Res 341 1282-1297... 

Heterocyclic compounds-Synthesis. 2. Carbohydrates. 3. Natural products-synthesis. 

Natural product synthesis is the centerpiece of organic chemistry because it has always been the ultimate testing ground for new concepts and new synthetic methods. " Despite recent advances in carbohydrate chemistry " and enzymatic glycosylation,giycopeptides and glycoproteins synthesis stands as one of... 

On the occasion of complex natural products synthesis, choice of the starting material(s) becomes a key for success of the aim in many cases. Along with well-designed retrosynthetic analysis and sophisticated synthetic schemes, availability of the starting materials, desirably in enantiomerically pure or enriched form, is an indispensable element. During these fifteen years we have extensively explored the stereoselective introduction of synthetically versatile carbon functionalities on the carbohydrate skeletons in hope of novel access to a variety of enantiomerically pure building blocks (so-called chirons ) [1-3]. For instance, we reported in 1985 that the thermal Claisen... 

The aldol strategy in Scheme 8b emanated from our interest in the alkylation of 39, a reaction which was explored in connection with our sugar-based approach to the polyquinanes (ref. 36). Thus, our application of carbohydrates for natural product synthesis has returned to benefit the carbohydrate domain in view of the new potential that it has opened for the... 

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