Corynantheidine-type alkaloids—I : Establishment of physical criteria for the normal, pseudo, allo and epiallo configurations by conformational analysis
✍ Scribed by W.F. Trager; Calvin M. Lee; A.H. Beckett
- Book ID
- 104202921
- Publisher
- Elsevier Science
- Year
- 1967
- Tongue
- French
- Weight
- 655 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0040-4020
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✦ Synopsis
Abatnct~orynantheidinc
-type alkaloids have thra asymmetric centrcs (C3. Cl& C20); the four possible con~urarion.s(cach an enantiotnorphic pair)can each exist in three ring D chair conformations. The twelve possibk chair conformations are subjected to conformational analysis to try to determine the preferred conformation(s) of each configuration. The analysis demonstrates one preferred conformation for each configuration whtch allows the aJsignmcnt of distinguishable physical properties (IR. NMR. ORD. CD) for the eight stereoisomers. Application of these physical criteria allows assignment of absolute configuration IO ring substrtuted or unsubstitutcd corynantheidinc-type alkaloids of unknown configuration. A COMPOL'ND of corynantheidine-type structure I has three asymmetric centres (C3, Cl5 and C20); this gives rise to the possibility of four conj~ururionr, viz. normal, pseudo, 0110 and epiullo (each of which can exist as an enantiomorphic pair). Furl hermore, each configuration can exist in threet different ring D chair conformurions due to inversion of the basic nitrogen atom and chair interconversion of ring D.
In this paper, conformational analysis is used to determine the most likely conformation(s) for each configuration. A unique set of physical criteria is deduced for the preferred conformation(s) which should permit configurational assignment to corynantheidine-type compounds of unknown stereochemistry. The physical criteria are compared with the physical data obtained from compounds of known absolute configuration' substantiating the conclusions and predictions reached herein; this information is then used to determine the absolute con!$uration of four Mirrugvnu alkaloids of corynanthcidine-type structure.t
The conformational analysis is based on the assumption that an estimation of l To whom inquires should be diruztod. t The conformation with a frmu dieriuf C/D ring junction is not posaibk.