Serendipitous synthesis of 3-hydroxy tetrahydrofurans from tin catalyzed sulfonylation of acyclic 1,2,4-triols
作者:Makhosazana P. Gamedze、Rejoice B. Maseko、Fidelis Chigondo、Comfort M. Nkambule
DOI:10.1016/j.tetlet.2012.08.110
日期:2012.10
The reaction of syn-1,2,4-triols under sulfonylation conditions catalyzed by Bu2SnO (5 mol %) results in cyclization and the formation of 3-hydroxy tetrahydrofurans (56-85%) while the anti-1,2,4-triols react to give C1-O-sulfonyl derivatives in good yields (66-83%) and the cyclization product in poor yield (5-12%). A mechanism that justifies these observations is proposed to occur via the tosylation of the primary hydroxyl followed by an intramolecular tin acetal rearrangement to a 1,3-stannylene which then undergoes a 5-exo-tet-cyclization. The difference in rates of cyclization reactivity is due to the energetically more stable tin acetals of syn-1,3-diols compared to those of anti-1,3-diols. (C) 2012 Elsevier Ltd. All rights reserved.
Synthesis of a spiroacetal moiety of antitumor antibiotic ossamycin by anodic oxidation
Synthesis of the spiroacetal moiety (C20–C33) of the antitumor antibiotic ossamycin, is reported. Anodic oxidation of the dithioacetal effected simultaneous removal of the protecting group and acetalization to afford the corresponding 6,6-spiroacetal structure in excellent yield.