Deprotection of silyl ethers by using SO3H silica gel: Application to sugar, nucleoside, and alkaloid derivatives

A Greener Technique for Microwave-Assisted O-Silylation and Silyl Ether Deprotection of Uridine and Other Substrates

A single clean, good-yielding, environment-friendly microwave-assisted procedure for O-silylation of uridine with tert-butyldimethylsilyl chloride (TBDMSCl), 1,8-Diazabicyclo(5.4.0)undec-7-ene (DBU) and potassium nitrate as catalyst under solvent-free conditions is reported. Subsequent silyl ether deprotection is accomplished with a reusable acidic resin via microwave irradiation. Both the silylation and desilylation protocols have been applied to a panel of alcohols of pharmaceutical interest.

Synthesis of β-Glucosides with 3-O-Picoloyl-Protected Glycosyl Donors in the Presence of Excess Triflic Acid: Defining the Scope

Excellent β-stereoselectivity for the glycosylation with glucosyl donors equipped with the 3-O-picoloyl (Pico) group, without the use of participating group, was achieved in the presence of NIS/excess TfOH promoter system. A complete investigation of the scope of this reaction was performed, revealing all important attributes of successful glycosylation. While altering the halogen source was tolerated, substitution of the triflate anion resulted in complete loss of stereoselectivity. Protonation of the Pico group was determined to be crucial in this reaction. The stability or extent of the protonated pyridine ring was also found to be another important key factor in obtaining high stereoselectivity. The nucleophilicity of the acceptor was found to be proportional to the stereoselectivity obtained, suggesting an S_N 2-like mechanism.