C-nucleosides, C-nucleoside precursors and a novel exocyclic glycal
Creators: name: Chow, Jack Kenny
Publisher: name: University of British Columbia
Year: 2010

description: The synthesis of 3-(R and S)-3,4-dihydroshowdomycin (171) and (170) and the novel 3-(S)-(2,3-0-isopropylidene-α-D-ribofuranosyl)succinimide [3-(S)-α-dihydroshowdomycin acetonide 176] are reported. Several functionalized C-glycosides along with the addition products of a novel exocyclic enolic sugar, methyl (E,Z)-4,7-anhydro-8-0-benzoyl-2,3-dideoxy-5,6-0-isopropylidene-D-ribo-oct-3-enonate (172), are also described. Application of the photoamidation reaction to methyl (E,Z)-4,7-anhydro-8-0-benzoyl-2,3-dideoxy-5,6-0-isopropylidene-D-allo-oct-2-enonate (18) yielded 3-(R,S)-(5-0-benzoyl-2,3-0-isopropylidene-β-D-ribofuranosyl)-4-hydroxy-4-methylpentanoic 1,4-lactone (139) and methyl 4,7-anhydro-8-0-benzoyl-3-C-carbamoyl-2,3-dideoxy-5,6-0-isopropylidene-D-glycero-D-allo (and altro) octonate (140) and (141). Cyclization of the 6-carbamoyl esters 140 and 141 with concomitant debenzoylation with sodium methoxide gave 170 and 171 after removal of the isopropylidene groups. Isomerization of the carbon-carbon double bond of 18 with sodium azide in a N,N-dimethylformamide solution gave 172 which when photoamidated and treated with sodium methoxide gave compound 176. Treatment of 18 with sodium azide gave methyl (E)-4,7-anhydro-8-0-benzoyl-2,3,5-trideoxy-g-erythro-oct-2,4-dienonate (178) along with 172. When excess hydrazoic acid was added to the above reaction mixture methyl 4,7-anhydro-3-azido - 8-0-benzoyl-2,3-dideoxy-5,6-0-isopropylidene-D-glycero-D-allo, altro-octonate (189) and small amounts of 172 were isolated. Reducing the amount of hydrazoic acid in the latter reaction gave compound 172 as the predominant product with small amounts of 189 along with methyl 3-amino-4,7-anhydro-8-0-benzoyl-2-diazo-2,3-dideoxy-5,6-0-isopropylidene-D-glycero-D-allo (and altro)-octonate (192) and (193), respectively. Hydrogenation of 189 in the presence of 5% palladium on carbon gave the corresponding amino compounds, methyl 3-amino-4,7-anhydro-8-0-benzoyl-2,3-dideoxy-5,6-0-isopropylidene-D-glycero-D-allo, altro-octonates (190) and (191), respectively. Hydrogenation of 192 and 193 as above in separate reactions gave the corresponding hydro-genolysis products 190 and 191, along with the hydrazones of methyl 3-amino-4,7-anhydro-8-0-benzoyl-3-deoxy-5,6-0-isopropylidene-D-glycero-D-allo (and altro)-2-octulosonate (195) and (196), respectively. The slow evaporation of the solvent from a diethyl ether-hexane solution of 172 or prolonged storage of 172 exposed to room atmosphere gave 5-0-benzoyl-2,3-0-isopropylidene-D-ribono-1,4-lactone (199), 8-0-benzoyl-2,3-dideoxy-5,6-0-isopropylidene-β-D-ribo-4-octulofuranosono-1,4-lactone (200), methyl (E)-8-0-benzoyl-2,3-dideoxy-5,6-0-isopropylidene-β-D-ribo-oct-2-en-4-ulofuranosonate (201), methyl 8-0-benzoyl-2,3-dideoxy-5,6-0-isopropylidene-β-D-ribo-4-octulofuranosonate (202), and methyl 8-0-benzoyl-2-deoxy-5,6-0-isopropylidene-α,β-D-allo (and altro)-4-octulofuranosonate (203) and (204), respectively. Treatment of 204 with para-toluenesulfonic acid in an azeotroping benzene solution yielded the furan derivative, 2-benzoyloxymethyl-5-(carbomethoxyacetyl)furan (212).