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Phytochemical investigation of the methanolic extract of the trunk bark of  Caloncoba welwitschii  (Oliv.) Gilg (Achariaceae) led to the isolation of four new compounds, including three new 30-norfriedelane triterpenes, welwitschiilactones D-F ( 1 – 3 ), one new friedelane triterpene, welwitschioic acid ( 4 ) as well as ten known compounds: stigmastane-3,6-dione (7), a mixture of  β -sitosterol and stigmasterol ( 6a  and  6b ), a mixture of  β -sitosterol and stigmasterol glucoside ( 11a  and  11b ), (2 S ,3 S ,4 R ,5 R )- N -(1,3,4,5-tetrahydroxyndecan-2-yl)tetradecanamide ( 10 ), 1- O - β - D- glucopyranosyl-(2 S ,3 R ,8 E )-2-[(2′ R )-2-hydroxylpalmitoylamino]-8-octadecene-1,3-diol (12), 3 β ,21 β -dihydroxy-27-oxo-30-nor-(D:A)-friedo-olean-20(29))en-27,19α-lactone ( 8 ), 21 β- hydroxy-3,27-dioxo-30-nor-(D:A)-friedo-olean-20(29)-en-27,19α-lactone ( 9 ) and 2 β ,21 β -dihydroxy-27-oxo-30-nor-(D:A)-friedo-olean-20(29)-en-27,19 α -lactone ( 5 ). The structures of all the isolated compounds were determined by extensive spectroscopic analyses (1D and 2D NMR as well as ESI-MS). The relative configuration of the 20-oxymethine in  1  as well as that of 19-oxymethine in  2  and  3  has been established using the NOESY spectrum. In an experiment, a sample of welwitschiilactone C ( 5 ) was chemically modified through reduction reaction to give a new hemi-synthetic derivative namely 2 β ,3 β ,21 β -trihydroxy-30-nor-(D:A)-friedo-olean-20(29)-en-27,19α-lactone ( 5a) .

Three new 30-norfriedelane and a new friedelane triterpenes from the trunk bark of Caloncoba welwitschii (Oliv.) Gilg (Achariaceae)