Monosaccharides asymmetric synthesis

The hetero-Diels-Alder cyclization reaction of tra s-l-methoxy-3-trimethylsilyloxy-1,3-butadiene (Si) (= Danishefsky s diene) with benzaldehyde (S ) (Scheme 12.23) [217-221] is a promising reaction for evaluating the catalytic properties of Lewis acidic lanthanide centers, and has enormous potential for asymmetric synthesis of natural products (e.g., monosaccharides) [222-225]. 

For reviews see (a) R. J. Fenier and S. Middleton, The conversion of carbohydrates into functionalized cyclopentanes and cyclohexanes, Chem. Rev. 95 2779 (1993) (b) K. J. Hale, Monosaccharides Use in asymmetric synthesis of natural products, Rodd s Chemistry of Carbon Compounds. Second Supplement to the 2nd ed. (M. Sainsbury, ed.), Elsevier, Amsterdam, 1993, Vol. 1E/F/G, pp. 315-435 (c) T. D. Inch, Formation of convenient chiral intermediates from carbohydrates and their use in synthesis, Tetrahedron 40 3161 (1984) (d) S. Hanessian, Total Synthesis of Natural Products The Chiron Approach Pergamon, New York, 1983. 

K. J. Hale, Monosaccharides Use in the asymmetric synthesis of natural products, Rodd s Chemistry of Carbon Compounds, 2nd ed., Vol. 1 EFG Second Suppl. (M. Sainsbury, ed.), Elsevier Science Publishers, Amsterdam, 1993, p. 315, and references therein. 

Hetero Diels-Alder Reaction. The hetero-Diels-Alder reaction involving glyoxylate as the dienophile provides an efficient access to the asymmetric synthesis of monosaccharides. The hetero Diels-Alder reaction with methoxydienes proceeds smoothly with catalysis by BINOL-TiCl2 to give the cis product in high enantiomeric excess (eq 14). The dibromide affords a higher cis selectivity, however, with a lower enantioselectivity, particularly in the trans adduct. The product thus obtained can be readily converted to the lactone portion of HMG-CoA inhibitors such as mevinolin or compactin. ... 

Monosaccharides as Chiral Auxiliaries and Ligands for Asymmetric Synthesis... 

Over the years, considerable efforts have been made toward the development of new synthetic routes to monosaccharides. Of particular interest is the de novo preparation of these carbohydrates (i.e., from achiral starting materials using asymmetric catalysis). While there are many uses of the term de novo in carbohydrate chemistry (5), herein the term de novo asymmetric synthesis refers to the use of catalysis for the asynunetric synthesis of carbohydrates from achiral compounds vide infra). 

Hale, K.J., Monosaccharides Use in the Asymmetric Synthesis of Natural Products in Rodd s Chemistry of Carbon Compounds, Vol. lE/F/G (Second Supplements to the second edition) Sainsbury, M., Ed. Elsevier Amsterdam, 1993. 

It might be presumed that by simple analogy, antibiotic monosaccharide 2-deoxy-L-fucose (14) could be best prepared from the corresponding hex-1-enitol (L-fucal), but scarce availability of the latter favors other routes. Total asymmetric synthesis from furan was elaborated by Vogel [50]. Alternative... 

A comprehensive review (260 refs.) on the synthesis of carbohydrates from noncarbohydrate sources covers the use of benzene-derived diols and products of Sharpless asymmetric oxidation as starting materials, Dodoni s thiazole and Vogel s naked sugar approaches, as well as the application of enzyme-catalysed aldol condensations. The preparation of monosaccharides by enzyme-catalysed aldol condensations is also discussed in a review on recent advances in the chemoenzymic synthesis of carbohydrates and carbohydrate mimetics, in parts of reviews on the formation of carbon-carbon bonds by enzymic asymmetric synthesis and on carbohydrate-mediated biochemical recognition processes as potential targets for drug development, as well as in connection with the introduction of three Aldol Reaction Kits that provide dihydroxyacetone phosphate-dependent aldolases (27 refs.). A further review deals with the synthesis of carbohydrates by application of the nitrile oxide 1,3-dipolar cycloaddition (13 refs.). ... 

Example 4.7 The asymmetric synthesis of optically pure aldol products 31-34 that on cycUzation in acidic medium afford dihydropyranones 35-38, important chiral intermediates in the synthesis of analogs of monosaccharides and other biologically active compounds, is presented in Scheme 4.15. 

In connection with the synthetic work directed towards the total synthesis of polyene macrolide antibiotics -such as amphotericin B (i)- Sharpless and Masamune [1] on one hand, and Nicolaou and Uenishi on the other [2], have developed alternative methods for the enantioselective synthesis of 1,3-diols and, in general, 1, 3, 5...(2n + 1) polyols. One of these methods is based on the Sharpless asymmetric epoxidation of allylic alcohols [3] and regioselective reductive ring opening of epoxides by metal hydrides, such as Red-Al and DIBAL. The second method uses available monosaccharides from the "chiral pool" [4], such as D-glucose. 

Part B discusses enantioselective natural product synthesis from monosaccharides. Nowadays, most natural product syntheses are performed in an asymmetric manner. This development is due principally to the realisation... 

In Part B, we analyse and discuss some recent enantiospecific natural product syntheses that have utilised monosaccharides as chiral starting materials. The coverage is not meant to be exhaustive or extensive but, rather, illustrative of the way in which monosaccharides are currently being used in asymmetric natural product synthesis. For more exhaustive coverage of this field, the reader is referred to several fine monographs and reviews.18... 

An example of the synthesis of a Cs-monosaccharide derivative (139) applying Sharpless asymmetric dihydroxylation is shown in Scheme 58 [268,269,270,271]. 

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