Comments on 'Piperidone derivative from Dalbergia sympathetica'.

Alcoholic extraction of Dalbergia sympathetica leaves yielded N-methyl-trans-4-hydroxy-L-proline and not 3,6-dihydroxy-N-methyl-2-piperidone, as previously reported. This is shown by the identity of the 1H and 13C NMR data of the isolated compound with those of N-methyl-trans-4-hydroxy-L-proline.