The structures offive naturally-occurring herbicidal nucleosides have been determined by spectral analysis. Three (5'-deoxyguanosine, coaristeromycin and 5'-deoxytoyocamycin) are novel natural products while the remaining two (coformycin and adenine 9-/?-D-arabinofuranoside) are known natural products which have not previously been reported to be herbicidal.
Microorganisms represent a well-documented source of herbicidal compoundswith the potential to provide agricultural researchers with new structural classes for herbicide synthesis efforts1*. In the continuation of a screening programto discover novel natural product herbicides from microbial sources2), Streptomyces rochei A13018 was found to produce ds-2-amino-l-hydroxycyclobutane-lacetic acid (CBAA: 1), which causes L-cysteineor L-methionine-reversible chlorosis in Arabidopsis thaliana. CBAA is a constituent of the naturally occuring antibacterial dipeptide (l S,2£> l-hydroxy-2-[(5)-valylamino]cyclobutane-l-acetic acid (2)3), and has been reported synthetically by Baldwin et alf^. However,no previous reports cite the isolation of CBAAas the free amino acid or describe its herbicidal properties. This note briefly describes the producing organism, fermentation, isolation, structure identification, and biological activities of CBAA. Strain A13018 was isolated from a soil sample collected in Madera Canyon, Santa Rita Mountains, Arizona, U.S.A. The aerial mycelium bore chains of spores forming spirals (S), as described by
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