Strychnos isostrychnine

Following the application of a Heck cyclization to a concise synthesis of the Strychnos alkaloid dehydrotubifoline [287, 288], and earlier model studies [289], Rawal employed a similar strategy to achieve a remarkably efficient synthesis of strychnine [290]. Thus, pentacycle 277 is smoothly cyclized and deprotected to isostrychnine (278) in 71% overall yield — an appropriate finale to this section ... 

Finally, in Rawafs total synthesis of ( )-strychnine, Heck cyclization of vinyl iodide 68 was employed to access the hexacyclic Strychnos alkaloid skeleton and deliver ( -) isostrychnine (69) in 74% yield [25J. Rearrangement in this case would not have been expected since the intermediate formed upon 6-exo closure would contain a particularly unstable tertiary C—Pd bond. The success of the transformation of 68 to 69 in spite of this potential obstacle is noteworthy. 

Sixteen alkaloids have been isolated from the seeds of Strychnos vomica L [82]. This journal (Acta Pharmaceutica Sinica) being difficult to access, we report in Table 4 the 13C NMR chemical shifts for 2-hydroxy-3-methoxystrychnine (12), isostrychnine (13), isobrucine (14), isostrychnine-Af-oxide (15) and isobrucine-Af-oxide (16) which are new compounds. 

New extractions of the root bark of Sri Lankan Strychnos nux vomica have disclosed the presence, besides strychnine, brucine, and isostrychnine, of 12-hydroxystrychnine, 12-hydroxy-11-methoxystrychnine, and a minor base, named protostrychnine (168), because of the obvious possibility that it may be an immediate biosynthetic precursor of strychnine. The overall structure (168), but not necessarily the configuration at C-17, was confirmed by allowing the 18-0-tigloyl ester to react with phosphorus oxychloride in pyridine saponification of the product, followed by treatment with dilute hydrochloric acid, then gave strychnine. 

Galeffi, C., Miranda-delUe-Monache, E., and Marini-Bettolo, G.B. (1974) Strychnos alkaloids. XXVII. Separation and characterisation of isostrychnine in Strychnos nux vomica L. seeds. Journal of Chromatography, 88, 416-418. 

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See also in sourсe #XX -- [ ]

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