Direct C-Glycosylation of Organotrifluoroborates with Glycosyl Fluorides and Its Application to the Total Synthesis of (+)-Varitriol

Abstract

A mild, stereoselective, and quick approach to accessing alkynyl and alkenyl C-glycosides via BF(3)·Et(2)O promoted coupling of organotrifluoroborates and glycosyl fluorides is reported. The application of this method was further demonstrated by the concise and efficient total synthesis of (+)-varitriol in only seven steps.

Identification and Characterization of Enzymes Catalyzing Pyrazolopyrimidine Formation in the Biosynthesis of Formycin A

“…18-24 Meanwhile, the forA gene (GenBank accession no. KY629733) was heterologously overexpressed and isolated as an N -terminal His 6 -tagged protein in Escherichia coli .…”

Synthesis of a C-phosphonate mimic of maltose-1-phosphate and inhibition studies on Mycobacterium tuberculosis GlgE

“…To deprotect the anomeric allyl group, we treated 4 with N -bromosuccinimide 13 . Instead of obtaining the reducing sugar 5 we obtained a bromo-substituted adduct (not shown) which was confirmed by ESI-MS. As an alternative, we treated 4 with palladium chloride in methanol to obtain 5 in 97% yield 14 . The target C-phosphonate 13 would have been accessed by a Horner-Wadsworth-Emmons 9 reaction mediated by tetramethyl methylenediphosphonate followed by global deprotection; however, the major product was the elimination product 7 .…”

Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

“…Recently, metal-free transformations involving organotrifluoroborates have emerged as an alternative to metal-catalyzed protocols [11]. More specifically, their Lewis acid-catalyzed reactions with stabilized carbocations such as iminium [12] and oxocarbenium ions [13][14][15][16] have been explored. However, the drawbacks to these methods are that they rely on the generation of unstable boron dihalide species thereby resulting in low functional group tolerance.…”