21-Deoxyajmaline

Tetraphyllicine [21-deoxyajmaline-19-ene, semperflorine ( )] rauvomitine (tetra-phyllicine-17-O-trimethoxybenzoate) mauiensine (17-epitetraphyllicine) purpeline (12-methoxytetraphyllicinone) mitoridine (12-hydroxytetraphyllicinone). 

Chart III. Degradation of deoxyajmaline and deoxyisoajmaline (epiineric C2o-ethyl). 

Bartlett et al. 191) reported the use of oxidative demethylation of LTA. When 21-deoxyajmaline-l7-( -acetate (304) was oxidized with LTA (1 equiv) in acetic anhydride, 2-hydroxy-21-deoxyajmaline-17-O-ace-tate (305) was produced. However, LTA oxidation (excess of the oxidant) in benzene of the acetate 304 proceeded via oxidative demethylation to give l-demethyl-A -2I-deoxyajmaIine-17-O-acetate (306), which was also... 

The chemical shifts for the 17-0-acetate methyl and the C-17 hydrogen and its coupling to the C-16 hydrogen were analogous with those recorded for 21-deoxyajmaline-17-0-acetate (6). 

A route (Chart IV) to the 4,21-seco-lO-deoxysarpagine system has been revealed (26a). Full details are not available at the time of writing, but it would seem that the concepts used in an earlier approach to strychnine (26b) have been used to construct a 4,21-seco-lO-deoxy-sarpagine system. An appropriate derivative of the latter has been converted to ajmaline, but it should be noted that in the critical conversion of the indole to the dihydroindole the principal product [see 21-deoxyajmalal-A->-21-deoxyajmaline (26c)] has the desired C-2 configuration. Full details of this work, especially with respect to stereoselectivity of a number of the steps, are to be published. 

Hobson JD, McCluske JG (1967) Cleavage of tertiary boses with phenyl chloroformate -reconversion of 21-deoxyajmaline into ajmaline. J Chem Soc C 2015-2017... 

Prefepential conversion. Deoxyajmaline treated 18 hrs. at 20° with phenyl chloroformate in methylene chloride phenyl 21-chlorodeoxydihydrochano-ajmaline-N(b)-carboxylate. Y 96%. - The iodo analog is obtained in 94% yield in the presence of LUiodide. - Similarly N-Methylpiperidine phenyl piperi-dine-N-carboxylate. Y 92%. - Phenyl chloroformate is more effective than the alkyl esters, and compares favorably with cyanogen bromide in efficacy as well as convenience. F. e. s. J. D. Hobson and J. G. McGluskey, Soc. (G) 1967, 2015. 

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