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Raocyclamides A and B, two novel oxazole-and thiazole-containing cyclic hexapeptides, were isolated from the cyanobacterium Oscillatoria raoi (TAU strain IL-76-1-2). The gross structures of raocyclamides A (1) and B (2) were elucidated by homonuclear and inverseheteronuclear 2D-NMR techniques and HREIMS. The absolute stereochemistry of compounds 1 and 2 was determined by Marfey's HPLC Method. Raocyclamide A (1) was established as cyclo-thiazole-D-Ile-oxazole-L-Ala-D-oxazoline-D-Phe and raocyclamide B (2) as cyclo-thiazole-D-Ile-oxazole-L-Ala-D-Ser-D-Phe. Raocyclamide A (1) exhibits a moderate cytotoxicity against sea urchin embryos.

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Afek, U., and Sztejnberg, A. 1988. Accumulation of scoparone, a phytoalexin associated with resistance of citrus to Phytophthora citrophthora.

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Multiple factors contributed to the outbreak of phytophotodermatitis. A late harvest in the south of the country is incriminated as the cause of the unusually high levels of psoralens in the celery of that year.