Bisbenzyltetrahydroisoquinoline alkaloids

Acylation (specifically, acetylation) of secondary nitrogens has occasionally been used to separate or characterize bisbenzyltetrahydroisoquinoline alkaloids, as in the case of tiliamosine (Section II,C, 138). O-Acetylation has been used principally as an adjunct to NMR studies of phenolic alkaloids. For example, comparison of thalictrogamine and its 0,0-diacetate enabled assignment of the hydroxys (209, Section VI,A,2,a). 

Secantioquine (512), C37H3gN2Og, amorphous, [a]D —15° (c 1, CHC13), was obtained from Pseudoxandra aff. lucida (Annonaceae). The structure was deduced from the UV base shift, NMR, and formation of secantioquine 0,O-diacetate by oxidation (KMn04/Me2CO) of the 0,0-diacetyl derivative of antioquine (466). Secantioquine is the first biphenyl-linked seco bisbenzyltetrahydroisoquinoline alkaloid (551,568). 

Bisbenzyltetrahydroisoquinolines. Biradicalic coupling (C 2.3.1) of two molecules of tetrahydroisoquinolines yields different types of dimeric alkaloids (cf. the formulas for tubocurarine and thalicarpine, Fig. 284). 

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