Chemical ecology of astigmatid mites. Part XXVIII. Hexyl 2-formyl-3-hydroxybenzoate, a fungitoxic cuticular constituent of the bulb mite Rhizoglyphus robini.

Abstract

The cuticular constituent of the bulb mite Rhizoglyphus robini is revealed to be hexyl 2-formyl-3-hydroxybenzoate (1) [hexyl rhizoglyphinate as the trivial name]. Structural proof of this novel ester relied on MS, GC-FTIR and NMR spectral data. The total synthesis of compound 1 was achieved in two steps, first by formylating methyl 3-hydroxybenzoate with hexamethylenetetramine in 75% polyphosphoric acid to give methyl 2-formyl-3-hydroxybenzoate, and then by a TsOH-catalyzed transesterification of the product with hexanol in benzene. Much higher antifungal activity than that of citral is demonstrated for compound 1, although its activity is lower than that of acaridials.