Osmylation sugars

See also J. S. Brimacombe, R. Hanna, A. K. M. S. Kabir, F. Bennett, and I. D. Taylor, Higher-carbon sugars. Part 1. The synthesis of some octose sugars via the osmylation of unsaturated precursors, J. Chem. Soc. Perkin Trans. 1, p. 815 (1986). 

Despite the high synthetic value of 1,2-amino alcohols, which are precursors of several therapeutically important sugar fragments, such as daunosamine, vancosamine and ristosamine, the osmylation of allylic amines or their derivatives often occurs with disappointing stereochemical results40 41. (Z)-Substituted allylic carbamates, however, show moderate syn selectivity105. A successful example is illustrated in the synthesis of l-benzyl-3,4-bis(benzyloxy)-5-(l,2-dihy-droxyethyl)pyrrolidine42. 

Similarly prepared by catalytic osmylation were cyclohexane derivatives54, tetrahydropyran derivatives55, several sugar derivatives56-57 and a tetrahydropiperidine derivative58,59. 

The C-glycoside 178 was used by Boyd and Sulikowski [87] in the total synthesis of enantiomerically pure urdamycinone B (182) and 104-2 (183) making use of the diene 107 derived from shikimic acid (Scheme 29) and the NMO oxidation to generate the C-5 phenols (Scheme 40). Thus, the bromonaphthoquinone 179 (prepared by treatment of phenol 178 with NBS) formed the tetracycle 180 through a Diels-Alder reaction with the diene 107 in analogy to sugar-free reactants. Osmylation to a cis-diol, deprotection, oxidation, and acetalization gave the acetonide 181. The decisive step in the aromatization to 182 and 183 was the reaction with NMO (Scheme 46). Aromatization was also effected by direct periodane oxidation of adduct 180 to derive 182 after deprotection. 

The diastereoselective synthesis of higher sugars was accomplished by bZi-osmylation of sugar derived dienes using OsO4-NMO4°. As shown in equation 23, osmylation of diene 26 afforded diastereomeric sugars 27, 28, and 29 in 90% overall yield in a 6.6 1.2 1.0 ratio, respectively. 

Acyclic Alditols. - Brimacombe s group have published full details of their work on the stereoselective synthesis of higher sugars, some of which is covered in Chapter 2 other papers describe the Sharpless oxidation of the octose derivative (1) to give the oxiran (2), and hence the D-erythro isomer (3), osmylation... 

Full details (see Vol. 24, p. 197, ref. 34) on the thesis of racemic arabino- and altro-, 5 itnino sugars by double osmylation of 1,2-dihydropyridines has been reported. ... 

The steric course of the osmylation of five higher sugar olefins, such as compounds 44 has been examined. Kishi s rule was I ound to be obeyed in all but one case (44, X,Y = O). ... 

In a total synthesis of mycalamide B, the aminal unit (63) was prepared from glucose derivative (61) via the key intermediates indicated in Scheme 14. Amongst much ingenious chemistry, the introduction of the axial dimethyl acetal grouping into (62) by the use of propargyl trimethylsilane-TMSOTf, followed by ozonolysis and acetalization, is noteworthy. Hydroxyl-ation of the allyl group involved asymmetric osmylation the synthesis was completed by acylation of (63) with a non-sugar-derived acid unit, and mycalamide A was made by a variation on the route.4... 

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