The paper reports the synthesis of some ethereal insect juvenile hormone analogs with a pinene or cyclohexene ring in the terminal position.
Synthese von Juvenilhormon-Analogen von Insekten, IV I). -Synthese von Ether-Analogen mit einem Pinen-und Cyclohexenring in der terminalen Stellung
Es wird die Synthese von Ether-Analogen von Insekten-Juvenilhormonen, die einen Pinenoder Cyclohexenring in der terminalen Stellung enthalten, beschrieben.
According to the literature2) compounds structurally related to natural insect juvenile hormones with an ethereal function in the molecule possess biological activity.
Extending our research on syntheses of juvenoids we obtained some ethereal juvenoids with a pinene (compounds a) or a cyclohexene (compounds b) ring in the terminal position. We synthesized ethyl (6) as well as isopropyl (7) esters of 3,7-dimethyl-10-(2-pinen-10-yl)-l0-oxa-2,4-decadienoic acid (a) and 1 1-(1-cyclohexenyl)-3,7-dimethyl-lO-oxa-2,4-undecadienoic acid (b) as well as ethyl esters of 3,7-dimethyl-l0-(2-pinen-l0-yl)-6,1O-dioxa-2-decenoic acid (10a) and 11 -(1 -cyclohexenyl)-3,7-dimethy1-6,1O-dioxa-2-undecenoic acid (10 b). Our syntheses were carried out according to Scheme 1.
Myrtenol (1 a) and 1-cyclohexenemethanol (1 b) were the starting materials in the presented syntheses. According to the general procedure used by Sorm et al. 3,4), these alcohols were treated with methyl vinyl ketone in the presence of red HgO and Et20 . BF3 to give the appropriate 5-oxaketones (2). The structures of these compounds were confirmed by IR and 'H NMR spectra. IR spectra show absorption bands at 1105 and 1720cm-' for the oxaketone 2a, and 1100 and 1710 cm-' for the oxaketone 2b, which are characteristic of C-0-C (ether) and C = 0 (carbonyl) functions, respectively. On the other hand, in 'H NMR spectra besides signals characteristic of the pinene and cyclohexene ring, a singlet is present at 6 = 2.0 (CH3C0 group). Furthermore, two triplets at F = 2.4 and 3.4 for C-3 and C-4 protons are present and a doublet at 6 = 3.6 for CH20 group protons.