Secophthalideisoquinolines

Article abstract of DOI:10.1021/jo00344a025

The secophthalideisoquinolines can be subdivided into enol lactones, keto acids, diketo acids, and ene lactams.The diastereomeric β- and α-hydrastine methiodides (8 and 9) supply stereoselectively Z and E enol lactones 11 and 12, respectively, in a syn β-elimination process.N-Methylhydrastine (11) reacts under mild conditions with methanol, water, or ammonia to produce keto ester 18, keto acid 17, or hydroxy lactam 36, respectively.Treatment of hydroxy lactam 36 with acid results in rapid loss of water and formation of the Z ene lactam 33.Photoequilibration of 33gives rise to a mixture of Z and E ene lactams 33 and 34.A biogenetic scheme is proposed for the secophthalideisoquinolines which includes the following sequence: classical phthalideisoquinoline -> phthalideisoquinoline N-metho salt -> secophthalide enol lactone -> secophthalide keto acid -> secophthalide diketo acid -> fumariflorine-type alkaloid.Ene lactams 30-33, as well as the hydroxy lactam fumschleicherine (35), are most probably artifacts of isolation.