5-Exo-dig Radical Cyclisation of 1,2,6-Trideoxy-6-iodo-L-arabino-hex-1-ynitols Derivatives

Abstract

Free radical cyclisation of the title iodides led to five-membered carbocycles in good yield. With 3,4-di-O-benzyl-l,2,6-trideoxy-6-iodo-L-arabino-hex-l-ynitol (9a), a three step process (5-exo-dig-cyclisation, [1,5] hydrogen atom transfer, fragmentation) resulted in extrusion of benzaldehyde giving mainly a mixture of (IS, 2R)-2-benzyloxy-4-methylene cyclopentan-1-ol (11a) and (1S, 2R)-2-benzyloxy-4-methylcyclopent-3-en-l-ol (12a). With 1,2,6-trideoxy-3,4-di-O-methyl-6-iodo-L-arabino-hex-l-ynitol (9b) or 1,2,6-trideoxy-6-iodo-L-arabinoa-hex-l-ynitol (9c), the expected (1S, 2S, 3S')-2,3-dimethoxy-4-methylene cyclopentan-1-ol (10b) or (1S, 2S, 3S)-4-methylenecyclopentan-l,2,3-triol (10c), were respectively obtained.