Proaporphines absolute configuration

Pakistanamine (46) was first characterized in 1973, and the absolute configuration was determined at C-6a, but not at C-13. In 1982, extensive proton NMR decoupling and NOE experiments (Section VI,A,2) were reported that made possible a complete stereochemical assignment of pakistanamine and, by extension, of five other (see Section II,C,6) benzylisoquinoline-proaporphine dimers. The protons of 46 were first assigned by spin decoupling of particular interest... 

The structure of imenine (72 R1 = R2 = OMe, R3 = R4 = Me, R5 = H), the first ketoaporphine alkaloid to have a substituent in the heterocyclic ring, was elucidated mainly by AT-ray analysis.92 The absolute configuration of S-( + )-isoboldine isolated from Corydalis pallida var. tenuis was assigned on the basis of o.r.d. and c.d. studies interestingly, all alkaloids isolated from this species belong to the S-series.97 The structure of the reduced proaporphine jaculadine... 

II) t3q>es. The absolute configuration of (-f )-norlaudanosine was elucidated by adopting a degradative method (isolation of i T-a-carb-oxyethyl-L-aspartic acid) 115), which in turn permitted the establishment of the absolute configuration of the proaporphine, aporphine, pro-morphinane, morphinane, and tetrahydroprotoberberine alkaloids (Scheme 20). The optical rotatory data 63), the ORD-curves 2, 41,120, 122), and the CD-curves 73) have led to an accumulation of sufficient information for the determination of the absolute configuration even of... 

The reduction with borohydride and the acid-catalyzed dienone-phenol/dienol-benzene rearrangements leave the center of chirality at C-6a intact. Consequently, the absolute configuration of this center can be intercorrelated with that of the benzylisoquinoline, proaporphine, and aporphine alkaloids (Schemes 1, 2, and 20). 

The proaporphine, promorphinane, and cularine alkaloids can be reconverted into the benzyltetrahydroisoquinoline bases with sodium in liquid ammonia, a process which permits correlation of the absolute configurations of the benzyltetrahydroisoquinoline, proaporphine, aporphine, promorphinane, and cularine alkaloids (375). 

The C-11 hydroxyl was tentatively assigned as being axial. Kesselringine shows negative CD Cotton effects at 250 and 300 nm, and a positive effect at 220 nm. By analogy with the reduced proaporphines, the absolute configuration of kesselringine was assumed to be as shown. ... 

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