2(E)-(4-Methyl-3-pentenyl)-butenedial, α-Acaridial, a Novel Monoterpene from the Acarid Mite Tyrophagm perniciosm (Acarina, Acaridae)

Abstract

A novel monoterpene, 2(E)-(4-methyl-3-pentenyI)-butenedial (α-acaridial (1) for the trivial name), was isolated from the secretion of the acarid mite Tyrophagus perniciosm. The structure was clarified in the light of spectral data, and the geometry of the double bond in the butenedial moiety was assigned based on the γ-deshielding effect on a methylene and on an aldehyde group. Coupling the Grignard reagent (CH₃)₂C=CHCH₂CH₂MgBr to THP-OCH₂(C=O)CH₂CH₂O-THP, and dehydration and deprotection of the OH groups gave α-(E)- and α-(Z)-acaridiol, which were fully assigned by MS and NMR. Matching the spectral data of the synthetic alcohols with those of the alcohol derived from the natural product, or of natural acaridial with those of synthetic α-(E)- and α-(Z)-acaridial, corroborated beyond all doubt the structure of this new monoterpene dial.