ChemInform Abstract: GLYCOSIDE SYNTHESIS USING 2,3,4,6‐TETRA‐O‐PIVALOYL‐α‐D‐GLUCOPYRANOSYL BROMIDE

Abstract

Die Glycosylierung von Benzylalkohol (IIa) bzw. Cholesterin (IIb) gelingt mit der Tetra‐O‐ pivaloylhalogenose (Ia) in Gegenwart von Ag‐Salzen in hoher Ausbeute.

SYNTHESIS OF 2-(TRIMETHYLSILYL)ETHYL α-d-MANNOPYRANOSIDES REVISITED

“…Solvent Table 2. 1H NMR Chemical Shifts a and Peak Multiplicities for Compounds 1,[5][6][7][10][11][12][13][14]16,18,19, mixtures slightly less polar than those used for TLC were used at the onset of elution. Chemical ionization mass spectra (CIMS, positive or negative ion) were obtained on a Finnigan 4000 quadrupole mass spectrometer with ammonia reagent gas.…”

“…TLC (5:1 hexane-EtOAc) then showed that the reaction was Table 4. 13 C NMR Chemical Shifts for Compounds 1,[5][6][7][10][11][12][13][14]16,18,19,[22][23][24] 3 20.65, 20.59, 20.51, 20.47. …”

“…[5] It has been suggested [5] that it is the hydrolysis of orthoesters, which are intermediates in glycoside formation from 2-O-acylated glycosyl donors, that causes the low yield of SE mannosides. Kunz [13] found that orthoester formation during glycosylation is suppressed when 2-O-pivaloyl glycosyl donors are used, unlike with other 2-O-acylated glycosyl donors. When we treated the fully pivaloylated 1-thioglycoside 13 with 2-(trimethylsilyl)ethanol (see Experimental), the desired, hitherto unknown, SE glycoside 14 was virtually the only product formed and, after chromatography, it was isolated crystalline in excellent yield of 87%.…”