| Popis: |
A Hofmann-type, oxidative rearrangement of methyl 4,6-O-benzylidene-3-C-carbamoyl-3-C-cyano-3-deoxy-α-d-glucopyranoside (1) by mercuric acetate and N-bromosuccinimide resulted in a 2-oxazolidinone ring fused to the pyranoside. Deoxygenation by tributylstannane of the 2-O-phenoxythio-carbonyl derivative of 1 led to its 2,3-dideoxy analog. The latter was subjected to Hofmann rearrangement with lead tetraacetate followed by reduction of the cyano group, with simultaneous N-tert-butoxycarbonylation in both steps, to give methyl 4,6-O-benzylidene-3-tert-butoxycarbonylamino-3-C-tert-butoxycarbonylaminomethyl-2,3-dideoxy-α-d-glucopyranoside. Hanessian reaction of this acetal yielded the corresponding 6-bromo-6-deoxy 4-benzoate which by dehydrobromination with DBU produced a blocked 3-C-aminomethyl-2,3,6-trideoxy-3,6-iminohexopyranoside. Methyl 3-amino-3,6-dideoxy-3-C-methoxycarbonyl-α-l-galactopyranoside was partially blocked atNH2-3 and OH-4 by N-tert-butoxycarbonylation and N,O-isopropylidenation, and then converted into a 2-xanthate. Subsequent Barton deoxygenation followed by hydride reduction of the methyl ester function and methylation of the resulting primary alcohol gave 3,4-protected derivatives of 3-amino 2,3,6-trideoxy-l- lyxo-hexose (l daunosamine) branched at C-3 by methoxycarbonyl, hydroxymethyl, and methoxymethyl groups. |
