Rhamnosylation: diastereoselectivity of conformationally armed donors

TY - JOUR

T1 - Rhamnosylation

T2 - diastereoselectivity of conformationally armed donors

AU - Heuckendorff, Mads

AU - Pedersen, Christian Marcus

AU - Bols, Mikael

PY - 2012/7/6

Y1 - 2012/7/6

N2 - The α/β-selectivity of super-armed rhamnosyl donors have been investigated in glycosylation reactions. The solvent was found to have a minor influence, whereas temperature was crucial for the diastereoselectivity. At very low temperature, a modest β-selectivity could be obtained, and increasing temperature gave excellent α-selectivity. The donors were highly reactive, and activation was observed at temperatures as low as -107 °C. Different promoter systems and leaving groups were investigated, and only activation with a heterogeneous catalyst increased the amount of the β-anomer significantly. By introducing an electron-withdrawing nonparticipating group, benzyl sulfonyl, on 2-O, an increase in β-product was observed.

AB - The α/β-selectivity of super-armed rhamnosyl donors have been investigated in glycosylation reactions. The solvent was found to have a minor influence, whereas temperature was crucial for the diastereoselectivity. At very low temperature, a modest β-selectivity could be obtained, and increasing temperature gave excellent α-selectivity. The donors were highly reactive, and activation was observed at temperatures as low as -107 °C. Different promoter systems and leaving groups were investigated, and only activation with a heterogeneous catalyst increased the amount of the β-anomer significantly. By introducing an electron-withdrawing nonparticipating group, benzyl sulfonyl, on 2-O, an increase in β-product was observed.

U2 - 10.1021/jo300591k

DO - 10.1021/jo300591k

M3 - Journal article

C2 - 22639871

SN - 0022-3263

VL - 77

SP - 5559

EP - 5568

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

IS - 13

ER -