Sharpless bishydroxylation

Pd-catalysed coupling of an o-iodophenol with an a,p-enyne features together with a Sharpless bishydroxylation in an enantioselective route to chromans of value in the synthesis of vitamin E <97SYN877>. An alternative approach to precursors of the tocopherol incorporates an asymmetric allylation <97SL1049>. A conversion of a-tocopherol to y-tocopherol involves the photo-decarboxylation of y-tocopherol-S-carboxylic acid <97SL208>. 

Vitamin E (a) L. F. Tietze, J. Gorlitzer, A. Schuffenhauer, M. HUbner, Eur. J. Org. Chem. 1999, 1075-1084. Enantioselective synthesis of the chromane moiety of vitamin E. (b) L. F. Tietze, J. Gorlitzer, Synlett 1997, 1049-1050. Preparation of enantiopure precursors for the vitamin E synthesis. A comparison of the asymmetric allylation of ketones and the sharpless bishydroxylation. (+)-Hydroxymyoporone (c) L. F. Tietze, C. Wegner, C. Wulff, Chem.-Eur. J. 1999, 5, 2885-2889. First total synthesis and determination of the absolute configuration of the stress factor (+)-hydroxymyoporone. 5,6-Dihydrocineromycin B (d) L. F. Tietze, L. Vblkel, Angew. Chem. Int. Ed. 2001, 40, 901-902. Total synthesis of the macrolide antibiotic 5,6-dihydrocineromycin B. 

As industrial important anodic addition reaction can be mentioned the synthesis of chiral 1,2-diols by indirect electrolysis. This reaction can be carried out, using a double mediator system consisting of ferricyanide and osmium tetroxide in the presence of chiral ligands. As an alternative to ferricyanide, electrogenerated iodine may be used. This reaction can be seen as an electrochemical variant of the asymmetric bishydroxylation introduced by Sharpless (Fig. 9-5). 

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