Synthesis of some carbahexopyranoses using Mn/CrCl3 mediated domino reactions and ring closing metathesis

Abstract

An efficient and common method for the synthesis of 5a-carba-α-d-mannopyranose 5, 5a-carba-β-d-mannopyranose 6, (+) methyl shikimate 9, (+) methyl-5-epi-shikimate 10, validamine analogue 15 and valiolamine analogue 16 from d-mannose, formal synthesis of Tamiflu 17 from d-ribose and also synthesis of 5a-carba-α-d-glucopyaranose 1, 5a-carba-β-d-glucopyaranose 2, 5a-carba-β-l-altropyranose 7 and 5a-carba-α-l-altropyranose 8 from d-xylose is described using Nozaki–Hiyama–Kishi (NHK) condition and ring closing metathesis (RCM). In this transformation 5-deoxy-5-halo-manno/ribo/xylo furanoside undergoes reductive elimination in the presence of Mn/CrCl3 to give corresponding olefin-aldehyde which was trapped by nucleophile under the same condition to afford diolefinic species which on metathesis reaction with appropriate Grubbs catalyst produced required carbocycles.