Carbohydrates in synthesis

Thesis

The use of carbohydrates as starting materials for organic synthesis is illustrated by the synthesis of several polyhydroxylated piperidine, pyrrolidine, indolizine and pyrrolizidine alkaloids.

Nucleophilic displacement by azide ion at C-2 in a D-glucose derivative, with subsequent intramolecular cyclisation through nitrogen onto the C-6 or C-5 position and functional group manipulation, led to the synthesis of: 1,5-dideoxy-1,5-imino-D-mannitol; 1,2,5-trideoxy-1,5-imino-D-arabinohexitol; 1,5-dideoxy-1,5-imino-D-glucitol; 2-Acetamido-1,5-imino-1,2,5- trideoxy-D-glucitol; 2-Acetamido-1,5-imino-1,2,5-trideoxy-D-mannitol; (2S, 3R, 4R, 5S)-3,4,5-trihydroxypipecolic acid; (2S, 3R, 4R, 5R)-3,4,5- trihydroxypipecolic acid and 2,5-dideoxy-2,5-imino-D-mannitol.

Nucleophilic displacement by azide ion at C-3 in a D-glucose derivative, with subsequent intramolecular cyclisation through nitrogen onto the C-6 position, produced the tosylate salt of 3,6-dideoxy-3,6-imino-1,2-0-isopropylidene- ⫏-D-glucofuranose, a highly divergent intermediate, from which the pyrrolidines: 1,4-dideoxy-1,4-imino-L-gulitol, 1,4-dideoxy-1,4-imino-D-lyxitol and (2S, 3S, 4R) - 3,4-dihydroxyproline were prepared directly. Periodate cleavage of the C1-2 bond and a 2-C chain extension from C-2 with subsequent intramolecular cyclisation, produced the pyrrolizidine (IS, 2R, 8R) - 1,2-dihydroxypyrrolizidine. An intramolecular Wadsworth Emmans cyclisation between a lactol at C-1 and a phosphonate, produced by a DCC coupling of the amine with dimethoxyphosphinylacetic acid, led to the formation of the indolizine (1S, 2R, 8S, 8aR) - 1,2,8-trihydroxyoctahydroindolizine.

The synthesis of 1,4-dideoxy-1,4-imino-D-lyxitol, was achieved by connection of C1 and C4 of a D-mannose derivative through nitrogen.

Methyl 3,5-0-isopropylidene- ⫏-D-xylofuranoside was elaborated to both enantiomers of 1,4-dideoxy-1,4-imino-arabinitol. The _D-enantiomer was produced by introduction of a nitrogen between C-2 and C-5, the L- enantiomer by introduction of a nitrogen between C-1 and C-4.

(2R, 3S, 4R) - 3,4-dihydroxyproline was prepared from _D-ribonolactone. The key step of the synthesis was a nucleophilic displacement by azide ion at C-2 in which the stereochemistry was unexpectedly retained.

Authors: Smith, P

• Peer review status: Peer reviewed
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford