Abstract
Synthesis and fungicidal activity of new six-membered cyclic phosphates were examined. Isothymol, thymol and eugenol in the essential oil of Alpinia speciosa K. SCHUM. possess strong antifungal activity against plant pathogenic fungi. 5-Alkyl-2-hydroxybenzaldehydes were prepared by Reimer-Tiemann reaction and reduced with NaBH4 to make 5-alkyl-2-hydroxybenzyl alcohols. 6-Alkyl-2-chloro-4H-1, 3, 2-benzodioxaphosphorin 2-sulfides were prepared by reacting these benzyl alcohols and PSCl3. Twenty-one kinds of six-membered cyclic phosphate were synthesized by reacting the 2-chloro derivatives and the components of essential oil. Among the prepared compounds, 6-ethyl-2-phenoxy-4H-1, 3, 2-benzodioxaphosphorin 2-oxide (13) showed the strongest activity, 38.5% at 10ppm against Pythium sp. For Corticium rolfsii, 6-isopropyl-2-methoxy-4H-1, 3, 2-benzodioxaphosphorin 2-sulfide (17) showed the strongest activity, 62.0% at 10ppm.
