Zwitterionic quinoniminium form

The second dimeric alkaloid conophyllidine (304) is identical in all respects with conophylline except for replacement of the epoxide function at positions 14 and IS of the tabersonine epoxide unit by a double bond. Conophylline has also been subsequently isolated from the South American species, Tabernaemontana glandulosa [182], and from the Thai species, Ervatamia microphylla [183]. It has also been reported from another Malaysian species, Ervatamia polyneura, under the name polyetvine [184]. The leaf extract of Ervatamia polyneura also yielded the related dimer, polyervininc (306), which is similar to conophylline except for the aromatic portion of the vincadifformine unit which now possesses an indoline dione chromophore, existing predominantly in its zwitterionic quinoniminium form. 

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See also in sourсe #XX -- [ ]

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