PREPARATION OFN-TERT-BUTOXYCARBONYLTHIOUREA OPENS THE WAY TO PROTECTED 2-AMINOTHIAZOLES

Abstract

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Preparation of 3,4-Substituted-5-Aminopyrazoles and 4-Substituted-2-Aminothiazoles

“…[268551-65-1]. 1 H and 13 C NMR spectra were consistent with those previously reported in the literature …”

“…Next, we focused on the synthesis of 4-boronic acid-2-aminothiazole MIDA ester, hoping that it would be sufficiently stable for purification (and easier handling). The MIDA-protected bromomethyl acylboronate was synthesized according to the published protocol from vinylboronic acid MIDA ester and used for condensation with N -Boc-thiourea 10 to provide the thiazole 11 (Scheme ). Subsequent protection with p -methoxybenzyl chloride afforded the desired MIDA ester 12 , which was stable to purification on silica gel and could be stored for months at room temperature under nitrogen (Scheme ).…”

Second-Generation Nitazoxanide Derivatives: Thiazolides are Effective Inhibitors of the Influenza a Virus

“…Reaction of bromoacetyl bromide 20 with sodium thioethoxide as described by Rao et al [15] afforded thioester 21 in very good yield. This intermediate was immediately reacted with N-t-butoxycarbonyl thiourea [16] in 2-propanol at 0-20 • C over 48 h, affording a good yield of the key intermediate 22 after chromatography. Addition of powdered 4Å sieves assisted this step by absorbing both water and HBr.…”

“…N-(t-butoxycarbonyl)thiourea [16] (2.90 g, 16.5 mmol) was added to solution of thioester 21 (2.96 g, 16.2 mmol) in isopropanol (30 ml) and stirred at 0 • C, then allowed to regain room temperature. After 16 h, an almost clear pale yellow solution had formed; freshly activated 4Å molecular sieves (1 g) were added and stirring continued for another 24 h. A mixture of EtOAc (50 ml) and half satd.…”