Stemona alkaloids stemocurtisine

New members of the Stemona alkaloids, stemona-amines C—E (24-26), were isolated (13TL6995). Research toward the synthesis of the Stemona alkaloid stemocurtisine was also undertaken and these efforts led to the diastereoselective construction of the linearly fused tricyclic core of the natural product by employing an aza-Wittig reaction to prepare the central azepine ring (13T8042).Total syntheses of the epimers of Stemona alkaloids... 

Stemokerrin (59) was isolated from the roots of 5. kerri (HG 889) and its relative configuration was firmly established by X-ray crystallography, which revealed the pyrido[l,2-n]azepine substructure and the Z configuration of the double bond at C12-C13, which is also present in other Stemona alkaloids, such as protostemonine (19) and stemofoline (48) (56). The presence of a 1 -hydroxypropyl substituent (or its O-methyl derivative) attached to C4 is another distinct feature of this group of Stemona alkaloids [except for stemocurtisine (58)]. Comparison of the C-NMR data of stemocurtisine (58)... 

Stemocurtisine Type Stemona Alkaloids Occurrence and Properties. 

The first alkaloid to be reported was stemocurtisine (58), isolated from the roots of 5. curtisii, the structure of which was established by X-ray crystallography. The piperidine ring adopts a chair-hke conformation, and it displays an ether bridge involving Cl and C9. The acetal-like nature of C9 is confirmed by the presence of a signal at 120.5 ppm in its C-NMR spectrum. The absolute configuration is not known, but it is assumed to be the same as the one in those alkaloids with the same C/D ring substructure [stemofoline (48)] (57). The same alkaloid was also isolated from the roots of Stemona sp. (56). 

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