A new Dieis-Alder-type adduct flavonoid from Dorstenia barteri

A new Dieis-Alder-type adduct, dorstenone (1), was isolated from Dorstenia barteri together with three known fiavonoids, 4,2',4'-trihydoxy-3'- prenylchalcone; 4,2',4'-trihydoxy-3,3'-diprenylchalcone; and 5,7,4'- trihydoxy-8-prenylflavone. The structure of 1 was elucidated using a combination of highfield NMR techniques, particularly, gradient-enhanced HMQC and HMBC

Urea derivatives from Pentadiplandra brazzeana

Four urea derivatives were isolated from the roots of Pentadiplandra brazzeana, and their structures were elucidated by spectroscopic techniques. N-Benzyl-N'-(4-methoxybenzyl)urea (1) is a new compound, although N,N'-di-(4- methoxybenzyl)urea (2), N,N'-dibenzylurea (3), and p-methoxythiobenzaldehyde (4) are reported from a natural source for the first time

Hosloppin, a new pyrone-substituted flavonoid from hoslundia opposita

Hosloppin [1], a new pyrone-substituted flavonoid, was isolated from the MeOH extract of the leaves of Hoslundia opposita. The structure of 1 was established as 3"-O-demethylhoslundin from an analysis of its spectroscopic data

Vernoguinosterol and vernoguinoside, trypanocidal stigmastane derivatives from Vernonia guineensis (Asteraceae)

Two bitter stigmastane derivatives, vernoguinosterol (1) and vernoguinoside (2), have been isolated from the stem bark of Vernonia guineensis and their structures eludicated using spectroscopic methods. The new compounds exhibit trypanocidal activity

Three labdane diterpenoids from Aframomum sceptrum (Zingiberaceae)

Three labdane diterpenoids, 8β,17-epoxy-3β,7β-dihydroxy-12(E)-labden-16,15-olide (1), methyl 8β,17-epoxy-3β,7β,15-trihydroxy-12(E)-labden- 16-oate (2) and 3β,7β,8β,12ζ,17-pentahydroxylabdan-16,15-olide (3) have been isolated from the seeds of Afromomum sceptrum K. Schum (Zingiberaceae) and their structures assigned on the basis of their spectroscopic properties. Nerolidol, and the known flavonoids 3-acetoxy-4′,5,7-trihydroxyflavanone, and 3,4′,5,7-tetrahydroxyflavanone were also obtained