Branched-chain sugars. Part 15. Synthesis of 1L-(1,2,3′,4,5/3,6)-3-hydroxymethyl-4,5-O-isopropylidene-3,3′-O-methylene-6-nitro-2,3,4,5-tetrahydroxycyclohexenecarbaldehyde dimethyl acetal, a potential key compound for total synthesis of optically active tetrodotoxin

Abstract

The Michael addition of 2-lithio-1,3-dithian to 5,6-dideoxy-3-C-hydroxymethyl-1,2-O-isopropylidene-3,3′-O-methylene-6-nitro-α-D-xylo-hex-5-enofuranose (6) obtained in seven steps from 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methylene-α-D-ribo-hexofuranose gave 5,6-dideoxy-5-C-(1,3-dithian-2-yl)-3-C-hydroxymethyl-1,2-O-isopropylidene-3,3′-O-methylene-6-nitro-α-D-glucofuranose (7) and -β-L-idofuranose (8)[(7) : (8)= 5 : 4] in ca. 60% yield. Intramolecular cyclization of both compounds after removal of the isopropylidene group gave branched-chain cyclitols with the muco-configuration (9)[from (7)] and the myo-configuration (13)[from (8)] respectively. The cyclitol (9) was easily converted into the desired title compound (12) in excellent yield.