Branched-chain sugars Claisen rearrangement

A well-developed concept to achieve high stereocontrol in the formation of a quaternary chiral center has been introduced by Fraser-Reid, using the Claisen rearrangement along two lines. In the first approach a type III branched-chain sugar is prepared by Wittig... 

An interesting procedure has been developed by Vat le to obtain C-5 branched-chain sugars [189]. It also takes advantage of the stereospecificity of the Claisen rearrangement of allyl (vinylsulfinyl) ether 158 derived from a 4,5-unsaturated sugar. An acrylic derivative 159 is formed in the process by elimination of sulfenic acid (Scheme 53). 

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. H. Baer and Z. S, Hanna, The preparation of amino sugars and branched-chain sugars by palladium-catalysed allylic substitution of alkyl hex-2-enopyranosides. Can. J. Chem. 59 889 (1981). D. P. Cuiran, An approach to the enantiocontrolled synthesis of pseudomonic acids via a novel mon-Claisen rearrangement. Tetrahedron Lett. 23 4309 (1982). 

Geminal Doubly Branched-Chain Sugars by Eschenmoser-Claisen Rearrangement 1157 ... 

An orthoester derived from the exocyclic unsaturated branched-chain sugar (41) underwent Claisen rearrangement to form the gem-disubstituted branched-chain sugar (42)(Scheme 14) the stereochemistry of (42) was deduced from the fact that the derived C-formyl sugar (43) did not form a hemiacetal. The 5-epimer of... 

The synthesis of branched-chain sugars by application of the Claisen rearrangement is noted in Chapter 12. 

A new approach to the preparation of a-branched-chain sugars by the Claisen rearrangement of hexenopyranoside allyl ethers has been reported (Scheme 24). Thus compound (68), on heating produces the axially substituted C-alkyl derivative (52) which can be epimerized to the equatorially substituted product with base. The rearrangement proceeds through a chair-like transition state as proved by the conversion of the E-crotyl ether derivative (69) to the tricyclic product (70). (See Scheme 11 for a different preparation of (52).)... 

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