Stemoamide group

S. tuberosa provided most of the isolated Stemona alkaloids, followed by S. japonica, and S. sessilifolia. The phytochemical study of Croomia is restricted to C. heterosepala and C. japonica, from which only two Stemona alkaloids were isolated [croomine (29) and didehydrocroomine (34)], both from the tuberostemospironine group (III). Alkaloids from the stemoamide group (II) were found in eight of the twelve investigated Stemona species, while the alkaloids from the other groups were isolated from only two to four Stemona species (Table XXV). 

In 1996, Mori reported the total synthesis of (—)-stemoamide through a ruthenium-catalyzed enyne metathesis developed by theit group (Scheme Enyne 83 prepared from (—)-pyroglutamic acid is reacted with Ic in... 

H-NMR Chemical Shifts (5, ppm) and Coupling Constants (/, Hz) for the Stemoamide Alkaloid Group. 

The tricyclic alkaloid stemoamide (15) is a typical representative of this group of Stemona alkaloids and it has been synthesized several times over the last few years, including some very efficient approaches. 

The first application of ene-yne RCM was reported in the total synthesis of the natural product (—)-stemoamide [8]. (—)-Pyroglutamic acid was converted into ene-yne 16 having an ester group on the alkyne, and RCM of ene-yne 16 was carried out in the presence of ruthenium-carbene complex [Ru]-I (4 mol%) to afford bicyclic compound 17 in 87% yield. Conversion of 17 into 18 followed by... 

---