Alkyl- and Acyl-Derivatives of Copsinine and Pseudocopsinine and Their Crystal Structures
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Acyl- and alkyl-derivatives at the N1 and N4 atoms, respectively, of the indoline alkaloids copsinine (1) and pseudocopsinine (2), which were isolated from the plant Vinca erecta, were synthesized. Alkaloids 1 and 2 reacted with alkyl halides to give N4 substitution; with acetic anhydride, N1. In turn, N1-acyl-1 and -2 reacted with alkyl halides to bond the alkyl radical to the N4 position. Reaction products were identified using IR spectroscopy and HPLC-MS. Their structures were elucidated by X-ray crystal structure analyses (XSAs). The tetrahedral hybridization of N1 in the indoline alkaloids was favorable for forming their N1-acetyl derivatives, which is improbable in indole and α-methyleneindoline alkaloids.
Keywordsindoline alkaloids copsinine pseudocopsinine Vinca erecta acylation alkylation XSA
The work was sponsored by the Basic Research Program of the Academy of Sciences of the Republic of Uzbekistan, Grant VA-FA-F6-010.
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