Cephalotaxine ester of 2-oxo-6-methylheptanoic acid was treated with lithium diisopropylamide and Me O-(1-methoxyisopropyl)glycolate to give a mixture of homoisoharringtonine (I) and its stereoisomers with 56% yield. The four stereoisomers separated by TLC showed identical mass spectra and almost superimposed IR but with different 1H NMR spectra. The configuration of the 2'-C and 3'-C of the four isomers were postulated based upon their 1H NMR spectra as compared with the 1H NMR spectra of isoharringtonine and its stereoisomers. The mixture of four stereoisomers exhibited antitumor activity against Leukemia L-7712 by inhibiting the synthesis of DNA.

Key words: ALKALOID, SEPARATION, ANTICARCINOGEN, PROTON MAGNETIC RESONANCE SPECTROMETRY, IDENTIFICATION, STRUCTURE AND PROPERTY CORRELATION, STEREOISOMERISM, CEPHALOTOXINUM