(+)-Physoperuvine, (±)-physoperuvine, and (+)-N,N-dimethylphysoperuvinium salt (anion unknown) were isolated from the roots of Physalis peruviana. Their structures were advanced on the basis of spectral and chemical evidence. These alkaloids comprise the first group of biogenetically interesting secotropane alkaloids. Elasnin (C24H40O4), isolated from the cultured broth of Streptomyces noboritoensis KM-2753, is a new specific inhibitor of human granulocyte elastase. Evidences based on spectral analyses, chemical degradations, and biosynthetic means using a 13C-labeled precursor established its structure as 1, having a highly alkylated 4-hydroxy-α-pyrone, rather than a 2-hydroxy-γ-pyrone, as the most likely skeletal structure. Structural comparison between elasnin and its methyl ether obtained by CH2N2 treatment was investigated, using UV data and 13C-13C couplings in both compounds biosynthetically enriched with [1,2-13C]acetate. Structural change from α-pyrone to γ-pyrone occured in the methylation of elasnin with CH2N2 but not in the acetylation with acetic anhydride in pyridine.