N-benzoylglycine/thiourea cooperative catalyzed stereoselective O-glycosidation: Activation of O-glycosyl trichloroacetimidate donors

Zinc Acetate Catalyzed Stereoselective 1,2-trans-Glycosylation Using Glycosyl Chlorides

“…17 Column chromatography purification using EtOAc : hexane (2:8) gave 4a as a white solid (-anomer only, 70 mg, 75%); 1 H NMR (500 MHz, CDCl3) δ 18H),2H),2H),2H),4.72 (d,J = 10.9 Hz,1H),3H),4.39 (d,J = 7.8 Hz,1H),3.97 (dt,J = 9.4,6.5 Hz,1H),3.74 (d,J = 10.7 Hz,1H),2H),2H),2H),2H),2H),6H), 0.88 (t, J = 7.0 Hz, 3H); 13 C NMR (100 MHz, CDCl3); δ 138. 7,138.5,138.2,138.1,128.3,128.1,128.0,127.9,127.8,127.6,127.6,103.7,84.7,82.3,78.0,75.7,75.0,74.9,74.8,73.5,70.2,69.0,31.7,29.8,25.9,22.6,3,4,6-tetra-O-benzyl--D-glucopyranoside 4d.…”

“…13 C NMR (125 MHz, CDCl3); δ 138.6, 138.5, 138.2, 138.1, 132.30, 128.39, 128.2,128.0, 127.9, 127.8, 127.69, 127.63, 125.3, 103.7, 84.7, 82.3, 77.9, 75.7, 75.0, 74.9, 74.8, 73.5, 69.8, 69.0, 31.5, 29.3, 28.0, 27.4, 22.6, 14 Prepared by the general procedure using 2,3,4,6-tetra-O-benzyl--D-glucopyranosyl chloride (0.15 mmol, 84 mg) and cyclopropylmethanol (0.18 mmol, 15 µl). 19 Column chromatography purification using EtOAc : hexane (2:8) gave 4j as a white solid (-anomer only, 57 mg, 64%). 13 C NMR (125 MHz, CDCl3); δ 138.…”

“…for C43H44NaO6, 679.3036.; found, 679.3037. 3 Prepared by the general procedure using 2,3,4,6-Tetra-O-benzyl--D-glucopyranosyl chloride (0.15 mmol, 84 mg) and cyclopropylmethanol (0.18 mmol, 15 µl). Column chromatography purification using EtOAc:Hexane (2:8) solvent system gave 4j as white solid ( only, 57 mg, 64%).…”

“…Optimization of the reaction parameters was explored using 2,3,4,6-tetra-O-benzyl-α-D-glucosyl halide (1a) 12 as the glycosyl donor and n-hexanol (2a) as the acceptor (Table 1). Most of the classical Lewis acids; ZnCl2, InCl3, Cu(OTf)2, Zn(OTf)2 failed to promote the glycosylation reaction at room temperature while, at higher temperatures, decomposition of the glucosyl halides was observed (Table 1, entries [1][2][3][4]. Interestingly, diethylzinc provided the desired 1,2-trans-glycoside product in moderate yield (Table 1, entry 5).…”

Organocatalysis applied to carbohydrates: from roots to current developments

“…Several glycosyl donors (gluco-, galacto-, or lacto-configured) or acceptors have been tested, yielding consistently the β-glycoside usually in very high selectivity. 29 Acid-sensitive protecting groups (such as isopropylidene) are stable under these conditions. However, when perbenzylated L-rhamnoside 45a was used, a reversal of selectivity was observed, affording the α-anomer 48a as the major product (albeit with moderate selectivity 1.5 : 1-2.5 : 1).…”