(2R,3S,4S)-2,3,4-trihydroxypentanal

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: There was added 5.0 g (37.3 mmoles) of 5-deoxy-L-(+)-arabinose obtained in Example to 80 ml of methanol and the mixture was stirred to give a clear solution. With stirring there was added dropwise 4.5 g (42 mmoles) of phenylhydrazine to the obtained mixture and thereto further a drop of glacial acetic acid was added. Thus obtained yellow solution was allowed to stand for 1 hour at room temperature and then the solution was evaporated under a condition close to vacuum as far as possible to give a thick viscous residue. After the residue was washed with 30 ml of ether twice, the residue was dissolved in 150 ml of ethyl acetate. The thus obtained solution was washed with about 40 ml of water twice, the organic layer was dried with sodium sulfate and the solvent was evaporated under vacuum. There remained a pale yellow skin-like solid on the bottom of the flask. The solid was washed with 30 ml of ether twice (for half an hour per each washing) and dried to give 8.0 g of 5-deoxy-L-arabinose-phenylhydrazone (yield: 96%). to give a clear solution With stirring there the solution was evaporated under a condition close to vacuum as far as possible to give a thick viscous residue After the residue was washed with 30 ml of ether twice the residue was dissolved in 150 ml of ethyl acetate The thus obtained solution was washed with about 40 ml of water twice the organic layer was dried with sodium sulfate the solvent was evaporated under vacuum The solid was washed with 30 ml of ether twice (for half an hour per each washing) and dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The compound (II) can be prepared by a similar process to the process for preparing 1',2'-diacetyl-L-biopterin [Bernard Schircks, Jost H. Bieri and Max Viscontini, Helvetica Chimica Acta, 60(1), 211 (1977)]. According to the process, L-rhamnose hydrate is reacted with ethanethiol. The obtained L-rhamnose-diethylmer-captal is converted to 5-deoxy-L-arabinose through 1,1-diethylsulfonyl-L-rhamnose. 5-Deoxy-L-arabinose is reacted with phenylhydrazine to obtain 5-deoxy-L-arabinose-phenylhydrazone. 5-Deoxy-L-arabinose-phenyl-hydrazone is reacted with an acylating agent. The obtained 2,3,4-triacyl-5-deoxy-L-arabinose-phenylhyrazone is reacted with 2,4,5-triamino-6-hydroxy-pyrimidine dihydrochloride, and then oxidized with an oxidizing agent such as iodine to obtain a 1',2'-diacyl-L-biopterin. L-Biopterin can be obtained by deacylation of the 1',2'-diacyl-L-biopterin.