An efficient, high-yielding Lewis acid promoted deprotection of O-trityl hydroxylamine derivatives is described. A range of acid-labile protecting groups, such as N-Boc and O-TBS, were tolerated under these mild conditions. The present method is applicable to the synthesis of a broad range of hydroxylamine derivatives, including N-hydroxy amides (hydroxamic acids), N-hydroxy sulfonamides, and N-hydroxy ureas, which often exhibit significant biological activities. An application of this methodology for a concise synthesis of (-)-Cobactin T (18) is also demonstrated.
In an effort to identify novel Janus kinase 3 inhibitors, a sequential focused screening approach was adopted to search our in-house chemical database. By biologically testing only 79 selected compounds, we successfully identified 19 compounds showing IC 50 < 20 microM, with four of them in the nanomolar range. Particularly, a 3,5-disubstituted pyrazolo[4,3- d]pyrimidine scaffold emerged as a promising candidate for further lead optimization. With the advantages of efficiency and flexibility, this approach may be utilized to identify leads for other therapeutic targets.
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