63569-19-7Relevant academic research and scientific papers
Chemical Transformations of Ajmalicine: Structure and Stereochemistry of Some Interchangeable Transformation Products
Chatterjee, Asima,Bandyopadhyay, Suchitra,Shoolery, J. N.
, p. 3113 - 3117 (1982)
Several chemical transformations were carried out with ajmalicine (1), a heteroyohimbine alkaloid, with a view to studying the reactivity of the enolic ester system occurring in the heterocyclic ring.Ajmalicine hemiacetal (2) and ajmalicine 17-methyl acetal (6) were prepared by treating 1 with aqueous and methanolic sulfuric acid, respectively.C-17 epimerization of 6 was observed in polar aprotic solvents, but this isomerization in 2 was prevented due to hydrogen bonding between vicinal carbomethoxy and hydroxy groups.Ajmalicial (12), the aldehydic derivative of 1, was prepared by following a new one-step pathway.Both cyclic (12) and open (14) forms of ajmalicial, a hemiacetal, were isolated and characterized.The cyclic form (12) was found to exist in an all-chair conformation (11).But for the open form (14) the most stable conformation (15) demands that the D ring must occur in a twist-boat form.This spatial orientation facilitated an electrophilic attack by the C-16 aldehyde group at C-7.The product was shown to be a new isomer (16) of ajmalicial having a 5,16-secoajmaline skeleton.The preferred conformation of 16 is 17.This new isomer was susceptible to protic solvents.LAH reduction of 1 afforded ajmalicinol (23).The structures and conformations of all these products could be established from spectral analyses including 13C NMR spectra.
ACID-CATALYSED RED-OX REARRANGEMENT OF A HEMIKETAL
Men, Jean Le,Zeches, Monique,Sigaut, Francoise
, p. 1807 - 1812 (2007/10/02)
Hemiketals 5a, b generated from the indole alkaloids ajmalicine 1a and tetraphylline 1b, yielded the isomeric hemiketals 7a,b upon acidic treatment.Ajmalicine 1a was converted in low yield to dihydrocorynantheol 10a through 7a.
