Total syntheses of (±)-glaziovine and (±)-pronuciferine by phenolic oxidative coupling

Abstract

Phenolic oxidative coupling of (i)-N-methylcoclaurine with potassium ferricyanide afforded (h) -glaziovine (111). whose methylation with diazomethane gave (*) -pronuciferine (VI). A very interesting dimeric compound (VIII) was also obtained.IT has been appreciated for many years that aporphine alkaloids could occur in Nature by phenolic oxidative coupling. Considering the biogenesis of roemerine (I) as an apparently abnormal alkaloid, Barton and Cohen proposed that the precursor, N-methylcoclaurine (11) , 7 Preliminary Communication, T.

Studies on the syntheses of heterocyclic compounds. 700. Syntheses of isoquinoline alkaloids with cuprous chloride and oxygen in pyridine as an enzymic model

“…The diether ( 16) had been previously obtained from oxidation of A-methylcoclaurine (17) with potassium ferricyanide. 35 It is interesting that oxidation of A-methylcoclaurine with oxygen-Cu2Cl2-pyridine yielded no corresponding proaporphine but rather tarry, unclarified products. One of the latter appeared to be a dimer of A-methylcoclaurine because after methylation with diazomethane, the mass spectrum of the crude product showed a peak at m/e 650.…”

Grandine A, a New Proaporphine Alkaloid from the Bark of Phoebe grandis

“…This could be due to either seasonal variations or a difference in the soil types (the former was collected from a lowland area while the latter was collected from a highland area). The occurrence of the new proaporphine in Phoebe grandis is of special interest, in view of the fact that this type of alkaloid is a precursor of aporphines [ 15 , 16 ] and proaporhine–tryptamines, found in Phoebe species. To the knowledge of the authors, only two oxoproaporphines have been previously reported; scortechiniine B ( 3 ) [ 11 ] and prooxocryptochine ( 4 ) [ 17 ].…”

Alkaloids

“…The simple isoquinoline alkaloids, such as salsoline (126), anhalamine (127), corypalline (128), thalifoline (129), and pilocereine (130), are tetrahydroisoquinolines substituted in the C-1 position by methyl, hydrogen, oxygen, or isobutyl groups. The stereochemistry of the optically active alkaloids is determined by conversion to an amino acid of known configuration.…”

“…The proaporphine alkaloids have been prepared by a variety of classical and biomimetic methods [127][128][129][130][131].…”