Gold Catalysis in Glycosylation Reactions

Abstract

Glycosylation of alcohols containing acid-sensitive groups, as for example 1,2-5,6-di-O-isopropylidene-glucofuranose, Fmoc-threonine tert-butyl ester or farnesol, is achieved using gly­cosyl trichloroacetimidates activated by gold(I) chloride (5-10 mol%). While glycosylation with 2-O-acyl protected glycosyl donors proceeds with 1,2-trans-selectivity, non-neighboring group active glycosyldonors give mixtures of anomeric glycosides or α-glycosides depending upon their structure and the reactivity of the glycosyl acceptor.

Key words

gold catalysis - glycosylation - glycosyl halide

References and Notes

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16

Analytical Data for Compounds 6, 8, and 10
Compound 6a: [α]_D ^²5 -38.2 (c 1, CHCl₃). ^¹H NMR (300 MHz, CDCl₃): δ = 4.52 (H-1, J _1,2 = 7.7 Hz). [¹8]
Compound 6b: [α]_D ^²5 28.1. ^¹H NMR (300 MHz, CDCl₃): δ = 4.51 (H-1, J _1,2 = 8.1 Hz).
Compound 8a: [α]_D ^²5 -5.1. ^¹H NMR (300 MHz, CDCl₃): δ = 4.51 (H-1, J _1,2 = 8.1 Hz). [¹9]
Compound 8b: [α]_D ^²5 -28.0. ^¹H NMR (300 MHz, CDCl₃):
δ = 4.48 (H-1, J _1,2 = 8.1 Hz).
Compound 8c: [α]_D ^²5 4.4. ^¹H NMR (300 MHz, CDCl₃): δ = 4.46 (H-1, J _1,2 = 7.7 Hz).
Compound 8d: [α]_D ^²5 -6.8. ^¹H NMR (300 MHz, CDCl₃): δ = 4.47 (H-1, J _1,2 = 8.1 Hz). [²0]
Compound 8e, β-anomer: [α]_D ^²5 11.3. ^¹H NMR (300 MHz, CDCl₃): δ = 4.97 (H-1, J _1,2 = 8.1 Hz).
Compound 8e, α-anomer: [α]_D ^²5 73.5. ^¹H NMR (300 MHz, CDCl₃): δ = 5.56-5.49 (m, 2 H, H-1, H-2). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 95.1 (C-1).
Compound 10a: [α]_D ^²5 25.6 (c 1, CHCl₃). ^¹H NMR (300 MHz, CDCl₃): δ = 5.32 (H-1, J _1,2 = 3.7 Hz).
Compound 10b: [α]_D ^²5 121.5 (c 1, CHCl₃). ^¹H NMR (300 MHz, CDCl₃): δ = 4.93 (H-1, J _1,2 = 3.7 Hz).