3,4-dihydro-2H-1-benzopyran-2-carboxylic acid → (R)-chroman-2-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

A solution of (+)-(R)-α-methylbelnzylamine (0.37 mol) in ethanol (100 ml) was added to a solution of 3,4-dihydro-2H-1-benzopyran-2-carboxylic acid (0.36 mol) in ethanol (200 ml). The mixture was allowed to crystallize out. The precipitate was filtered off and dried. The residue was crystallized 4 times from ethanol. The precipitate was filtered off and dried. The residue was taken up in water, treated with HCl 10% and extracted with diethyl ether. The organic layer was separated, dried, filtered and the solvent was evaporated, yielding 8.6 g of (−)-(R)-3,4-dihydro-2H-1-benzopyran-2-carboxylic acid (mp. 85.5° C., [α]D20=−6.7° (c=100 mg/10 ml in methanol)) (interm. 1).

Herkunft & Nachweise