Carbohydrates, branched-chain synthesis

H. Santos, Construction of a branched chain at C-3 of a hexopyranoside. Synthesis of miharamycin sugar moiety analogues, Carbohydr. Res., 325 (2000) 1-15. 

A useful application of the chemistry shown in Scheme 83 is the synthesis of branched-chain functionalized carbohydrates. For this purpose two epoxides 261 and 262 derived from D-glucose and 263 derived from D-fructose were prepared following reported methodologies, and were submitted to a DTBB-catalyzed lithiation as described above in Scheme 83. The expected intermediates 264-266 and final products 267-269 were prepared in a regio- and stereoselective manner in 15- 95% yield" Also here, the use of a prochiral electrophile gave equimolecular amounts of both diastereomers. 

Five-membered lactones (y-butyrolactones) fused to carbohydrates have proven to be convenient synthons towards branched-chain sugars through opening of the lactone unit. Velaskes et al. [208] described the synthesis of y-butyrolactones... 

The substantial progress made in synthesis of the complex carbohydrates occurring in medicinally important molecules68-72 is largely due to the discovery of new oxidative procedures that permit ready preparation of aldosuloses. Branched-chain sugars were obtained by nucleophilic additions to various lcetopentoses and ketohexoses subsequent condensation with purines and pyrimidines then afforded the desired natural, or synthetic, antibiotics (see, for example, Refs. 19 and 73). 

Occurrence in nature of branched-chain carbohydrates has prompted interest in the syntheses of these complex structures and stimulated the preparation of analogues for biological evaluation. Consequently, new methods for the construction of these particular skeletons have been devised [1]. The use of carbohydrates as a cheap source of chiral starting materials [2-4] for the synthesis of complex, nonsugar molecules has prompted the emergence of new imaginative methods for formation of carbon-carbon bonds adapted to the particular reactivity of sugar moieties. 

The synthesis of vicinal doubly substituted carbohydrates can be achieved, as mentioned earlier, by successive formation of simple branched-chain carbohydrates. Other methods have emerged that are mostly based on the formation of 3-, 4-, 5-, or 6-membered ring fused to a pyranose-furanose ring. This process allows high stereocontrol on the two newly... 

J. Yoshimura, Synthesis of branched-chain sugars, Adv. Carbohydr. Chem. Biochem. 42 69 (1984). 

D. Horton and E. K. Just, Stereospecific chain-branching by C-alkylation at the ketonic and enolic positions of l,6-anhydro-2,3-0-isopropylidene-beta-D-lyxo-hexopyranos-4-ulose, Carbohydr. Res. IS 81 (1971). D. C. Baker, D. K. Brown, D. Horton, and R. G. Nickol, Synthesis of branched-chain sugar derivatives related to algarose, Carbohydr. Res. 32 299 (1974). 

H. Paulsen, V. Sinnwell, and J. Thiem, Applications of the 1,3-dithiane procedure for the synthesis of branched-chain carbohydrates. Methods Carbokydr. Chem. 8 185 (1980). 

J. S. Brimacombe, J. A. Miller, and U. Zakir, An approach to the synthesis of branched chain amino sugars from C-methylene sugars, Carbohydr. Res. 49 233 (1976). 

R. J. Ferrier and N. Vethaviyasar, Unsaturated carbohydrates. Part XVII. Synthesis of branched-chain sugar derivatives by application of the Claisen rearrangement, J. Chem. Soc. Perkin Trans, p. 1791 (1973). 

H. Feist, K. Peseke, and P. Koll, Synthesis of branched-chain sugars with methiniminium, Carbohydr. Res. 247 315 (1993). 

Carbohydrate chemistry is engaged in the synthesis and variation of deoxy sugar chains, where a wide set of protective groups and stereoselective glycosylation techniques are required. This contribution centers on stereoselective syntheses of mono-and oligosaccharides in the field of 2,6-dideoxy- and, in particular cases, branched-chain sugars, and summarizes modem synthetic glycosylation reactions which have been developed for this special kind of carbohydrate chemistry. 

J. Yoshimura, N. Kawauchi, T. Yasumori, K. Sato, and H. Hashimoto, Branched-chain sugars. 37. Synthesis of 2,3-anhydro-hexopyranosides and 3,4-anhydro-hexopyranosides having a methyl branch on the oxirane ring, and their reactions with some lithium methylcuprate reagents, Carbohydr. Res., 133 (1984) 255-274. 

I. I. Cubero and M. T. P. Lopez-Espinosa, Branched-chain sugars. 12. Synthesis of 3,4-anhydro-l-deoxy-3-C-methyl-D-hexulose derivatives, Carbohydr. Res., 154 (1986) 71-80. 

T. D. Inch and G. J. Lewis, The synthesis of branched-chain, deoxysugars by sugar epoxide-Grignard reagent reactions, Carbohydr. Res., 15 (1970) 1-10. 

A.-M. Sepulchre, G. Lukacs, G. Vass, and S. D. Gero, Synthesis and pulse Fourier transform 13C NMR spectra of branched-chain carbohydrates, Angew. Chem. Int. Ed., 11 (1972) 148. 

Addition of Pseudohalogens to Unsaturated Carbohydrates. Part III. Synthesis of 3-Deoxy-3-C-nitromethyl-D-allose, a Branched-chain Nitro Sugar, W. A. Szarek, J. S. Jewell, I. Szczerek, and J. K. N. Jones, Can.]. Chem., 47 (1969) 4473-4476. 

Considerable work was done to induce chirality via chiral auxiliaries. Reac tions with aromatic a-ketoesters like phenylglyoxylates 21 and electron-rich al kenes like dioxoles 22 and furan 23 were particularly efficient (Scheme 6). Yield up to 99% and diastereoselectivities higher than 96% have been observed whet 8-phenylmenthol 21a or 2-r-butylcyclohexanol 21b were used as chiral auxiliarie [14-18]. It should be noted that only the exoisomers 24 and 25 were obtained from the reaction of dioxoles 22. Furthermore, the reaction with furan 23 wa regioselective. 24 were suitable intermediates in the synthesis of rare carbohydrate derivatives like branched chain sugars [16], Other heterocyclic compounds liki oxazole 28 [19] and imidazole 29 [20] derivatives as well as acyclic alkenes 3fl 31, and 32 [14,15,21,22] were used as olefinic partners. Numerous cyclohexane derived alcohols [18,21-24] and carbohydrate derivatives [25] were used as chiri... 

Overend, W G, White, A C, Williams, N R, Branched-chain sugar Part XII. Branched-chain sugars derived from methyl 2,3-0-isopropylidene-p-L-ery/hro-pentopyranosid-4-ulose, and a synthesis of L-apiose, Carbohydr. Res., 15, 185-195, 1970. 

Yunker, M B, Plaumann, D E, Fraser-Reid, B, The stereochemistry of conjugate addition of lithium dialkyl cuprate reagents to some carbohydrate a-enones. Can. J. Chem., 55, 4002-4009, 1977. Baer, H H, Ong, K S, Raeactions of nitro sugars. IX. The synthesis of branched-chain dinitro sugars by Michael addition. Can. J. Chem., 46, 2511-2517, 1968. 

Chapleur, Y, Chretien, F, Selected methods for branched-chain carbohydrates synthesis. In Modern Synthetic Methods in Carbohydrate Chemistry, Hanessian, S, Ed., Marcel Dekker, New York, pp. 207-252, 1996. 

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