(+)- and (-)-syn-2-isobutyl-4-methylazetidine-2,4-dicarboxylic acids from the extract of Monascus pilosus-fermented rice (Red-Mold Rice)

The structures of two enantiomeric azetidine-type amino acids isolated from the n-butanol-soluble fraction of the 70% ethanol extract of red-mold rice fermented with Monascus pilosus were established to be (+)-[1; (+)-monascumic acid] and (-)-syn-2-isobutyl-4-methylazetidine-2,4-dicarboxylic acids [2; (-)-monascumic acid] based on spectroscopic methods.