Strain W5 was isolated from stem of Trewia nudiflora L. and identified as a member of Streptomyces according to its 16S rDNA partial sequence. From extracts of fermentation medium of W5, a new γ-butyrolactone (1), together with nine known compounds [2-methyl-2,5-bornandiol (2), dimeric dinactin (3), (R)-2-((2R,5S)-tetrahydro-5-(2-oxopropyl)furan-2-yl)propanoic acid (4), 2-(5-(2-acetoxypropyl)-tetrahydrofuran-2-yl)propanoic acid (5/6), (±)-homononactic acid (7/8), (±)-nonactic acid (9/10)] was isolated. Their structures were elucidated on the basis of extensive spectroscopic data.

To determine the biosynthesis pathway of the atisine-type diterpenoid alkaloids spiramines A/B and C/D, feeding experiments in in vitro cultured plantlets and enzymatic transformations in cell-free extracts were performed in combination with LCMS and tandem MS analyses. l-[2-13C,15N]Serine was used in the feeding experiments and enzymatic transformations, and the diterpene spiraminol was identified as a biosynthetic precursor of spiramine alkaloids. The LCMS and tandem MS spectra of the extracts from these experiments indicated that l-[2-13C,15N]serine was incorporated into spiramines A/B and C/D. The labeled reaction products show that l-serine is the one possible nitrogen source involved in the biosynthesis of atisine-type DAs.