Stemona alkaloids stemofoline group

Stemona alkaloids. Root extracts of the medicinal plants Stemona japonica and S. tuberosa (Stemona-ceae) have been used in Chinese and Japanese folk medicine as insecticides, anthelmintics, and as drugs for the treatment of tuberculosis, bronchitis and pertussis. Responsible for the activities is a group of more than 20 polycyclic alkaloids with diverse structures, e.g. protostemonine CjsHsiNOj, Mr 417.50, mp. 172-173 °C, [alD +148° (CH3OH) and stemofoline. 

There are also several examples of imidate-derived azomethine yhdes reported in the Hterature. For example, the Gin group described a clever use of these 1,3-dipoles in an approach to the azatricychc core of some stemofoline members of the stemona alkaloid family. The formation of the azomethine ylide 164 occurred upon exposure of pyrroUdine 163 to triflic anhydride and tetrabutylammonium triphenyldifluorosihcate (TBAT Scheme 35) (2008T3629). Cycloaddition of the resulting dipole across the pendant vinyl sulfide fiomished 165 in 71% yield. Enol triflate 165 was then reduced to give the saturated side chain in 166 in 89% yield by the action of Pd/C under an H.2 atmosphere. The enolate derived from 166 was treated with ethyl iodoa-cetate in the presence of hexamethylphosphoramide (HMPA) followed by... 

The stemofoline group comprises some of the structurally more complex representatives of the Stemona alkaloids, and currently ten alkaloids have been described stemofoline (48) 17,22,53,54), oxystemofoline (49) (77), methoxystemofline (50) (77), 2 -hydroxystemofoline (51) 22,36), 16,17-didehydro-16( )-stemofoline (52) 22,54), also named as didehydrostemofoline, l, 2 -didehydrostemofoline or asparagamine A (5,55),... 

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)... 

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