Platycerine

The total synthesis of pavinane alkaloid platycerine (89) (Scheme 14) has been accomplished successfully (26) via 1-benzylisoquinoline derivative 91 obtained from Reissert intermediate 90. Quatemarization of 91 with methyl iodide followed by lithium aluminum hydride reduction supplied 1,2-dihydroisoquinoline 92, which on treatment with a 7 5 mixture of formic acid and phosphorous acid gave ( )-platycerine (89) in 60-70% yield. 

Platycerine (14) Papaveraceae Fisch. et Lall. Argemone gracilenia 35... 

Section V,B)- The upfield shift of the H-6 to 8 4.35 and the downfield shift of H-9 to 8 6.43 on acetylation were in conformity with what has been observed on acetylation of the phenolic monomeric pavine base, (—)-platycerine (14). 

The second dimeric base, (—)-pennsylpavoline (179), was shown to correspond to C-l-demethylpennsylpavine. Specifically, its NMR spectrum was devoid of the 8 3.71 singlet which represents the C-1 methoxyl absorption in (—)-pennsylpavine (178). Evaluation of CD spectra of these novel dimers and comparison with those of the aporphine (+)-A -methyllaurotetanine and the pavine (—)-platycerine led to the assignment of the absolute configurations as depicted in expressions 178 and 179. These dimers are probably derived biosynthetically from the aporphine-benzylisoquinoline dimers, (-)-pennsylvanine and (-)-pennsylvanamine, which were found in the same plant (7,173). 

C20H23O4N Cory dine Isocorydine lsonorargemonine O-Methylisoboldine N-Methyllaurotetanine Norargemonine Platycerine... 

Alkaloid AP-1, (-)-argemonine methohydroxide, (-)-o-canadine methohydroxide, chelerythrine, corysantine, cyclanoline [= (-)-a-scoulerine methohydroxide], magnoflorine, (-)-platycerine methohydroxide, (-)-stylopine methohydroxide Bisnorargemonine, munitagine... 

The pavine alkaloids bisnorargemonine (54d) (566, 567), norargemonine (54e) (568), eschscholtzidine (54f) (569), platycerine (55b) (570), munitagine (55a) (571), and the newly isolated 2,9-dimethoxy-3-hydroxy-pavinane (54c) (221) were prepared synthetically. Studies of the reaction conditions of the synthesis led to an increase in the yields of pavinane... 

Scheme 20. Possible biosynthetic pathways (20) ofpavine alkaloids. Alkaloids found in A gracilenta are italicized. Path A, in A. munita and A. hispida path A, an alternative cyclization from (+)-reticuline to munitagine in A. gracilenta path B, in A. gracilenta path B, an alternative cyclization from laudanidine to platycerine.

The aerial parts of Argemone platyceras yielded the quaternary alkaloids (—)-platycerine melhohydroxide (72 R = OH, = H) and (—)-argemonine methohydroxide (72 R = H, R = OMe). A. munita subsp. rotundata has been shown to elaborate a new alkaloid, 3-hydroxy-2,9-dimethoxypavinane (73),... 

The pavines platycerine and isonorargemonine have been isolated from Thalic-trum revolutum. ( )-Caryachine (51 R = H, R = Me) and the isomeric base (51 R = Me, R = H) have been synthesized by cyclization of the appropriate 1,2-dihydroisoquinolines. ... 

Platycerine A -metho salt Argemone platyceras Link Otto... 

Stermitz and his collaborators constructed the benzylisoquinoline methiodides necessary for conversion to the unsymmetrically substituted pavines platycerine and munitagine by way of a Reissert compound. Alkylation of the Reissert compound derived from the isoquinoline 2 with the appropriately... 

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