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2005
Carbohydrates
U 0500
Applying Asymmetric Dihydroxylation to the Synthesis of Difluorinated CarboAnalogues: A 1,1-Difluoro-1-deoxy-D-xylulose. — A synthetic access to25- 193 hydrate
wards difluorinated carbohydrate analogues is presented, involving the Stille reaction
to construct the difluorodienes which should then undergo Sharpless asymmetric dihydroxylation followed by cyclization. The Stille reaction proceeds with a variety of substrates to give dienes like (III) or (XVI), but the following dihydroxylation step is
strongly influenced by the substrate structure. Thus, asymmetric dihydroxylation of
p-methoxybenzoyl-protected hydroxydiene (III) and carbamate (XVI) proceeds readily
with excellent enantioselectivity while conjugated dienes (XVIII) remain unchanged
under analogous reaction conditions. Furthermore, the base-induced transacylation—metal enolate formation to close the carbohydrate ring is not achieved for derivative (XVII) but cyclization of enol acetal (VII) and enol ether (XI) is successful. —
(COX, L. R.; DEBOOS, G. A.; FULLBROOK, J. J.; PERCY*, J. M.; SPENCER, N.;
Tetrahedron: Asymmetry 16 (2005) 2, 347-359; Dep. Chem., Univ. Leicester,
Leicester LE1 7RH, UK; Eng.) — Mischke
2005
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