Anthony J. Rollins

Syntheses of methyl 2,3,6-trideoxy-α-L-erythro-hexopyranoside (methyl α-L-amicetoside) and methyl 2,3,4,6-tetradeoxy-4-(dimethylamino)-α-L-threo-hexopyranoside (methyl α-L-ossaminide)

Methyl 2,3,6-trideoxy-α-L-erythro-hexopyranoside (12), the free sugar of which is enantiomeric with a constituent of the antibiotic amicetin, has been synthesized in three steps from 3,4-di-O-acetyl-L-rhamnal (7) by its rearrange-ment to, inter alia, methyl 4-O-acetyl-2,3,6-trideoxy-α-L-erythro-hex-2-enopyranoside (8) with boron trifluoride in dichloromethane–methanol. Deacetylation and hydrogenation of the latter compound gave the required product (12). Methyl 2,3,6-trideoxy-4-O-methylsulphonyl-α-L-erythro-hex-2-enopyranoside (15) underwent ready SN2 displacement of the allylic sulphonate group to give the 4-azide (16), which on hydrogenation and N-dimethyl-ation gave methyl 2,3,4,6-tetradeoxy-4-(dimethylamino)-α-L-threo-hexopyranoside (17). The free sugar liberated from the latter glycoside is enantiomeric with a sugar component of the spiramycin antibiotics.

Branched-chain sugars. Part V. Identification and synthesis of vinelose

6-Deoxy-2-O,3-C-dimethyl-L-talose (24) has been synthesised from 1,2-O-isopropylidene-3-C-methyl-α-D-allofuranose (3) and shown to be identical with vinelose, a component of two cytidine nucleotides isolated from Azotobacter vinelandii strain O.

Branched-chain sugars. Part III. Synthesis of D-nogalose (6-deoxy-3-C-methyl-2,3,4-tri-o-methyl-D-mannopyranose)

D-Nogalose [D-(1)], the enantiomer of a sugar component of the antibiotic nogalamycin, has been synthesized in seventeen steps from methyl α-D-glucopyranoside. The C-methyl substituent was introduced by addition of methylmagnesium iodide to 1,2:5,6-di-O-isopropylidene-β-D-arabino-hexofuranos-3-ulose (15). A related attempt to prepare L-nogalose (1) from 1,2:5,6-di-O-isopropylidene-α-D-xylo-hexofuranos-3-ulose (2) was unsuccessful, since configurational inversion at C-5 could not be achieved at a later stage of the synthesis.

Syntheses of derivatives of L-tolyposamine and L-forosamine

Methyl 4-benzamido-2,3,4,6-tetradeoxy-α-L-erythro-hexopyranoside (methyl N-benzoyl-α-L-tolyposaminide)(6) and methyl 2,3,4,6-tetradeoxy-4-dimethylamino-α-erythro-hexopyranoside (methyl α-L-forosaminide)(7) have been synthesized by way of an iodide displacement on the allylic sulphonate, methyl 2,3,6-trideoxy-4-O-methylsulphonyl-α-L-erythro-hex-2-enopyranoside (3), followed by an azide displacement on the resulting iodide (4).