Hydrogen Peroxide → HCID 11536278, compound

##STR22## This compound is the major attractive component of the pheromone of the western pine beetle, Dendroctonus brevicomis. The present synthesis began with the ethylene ketal of 5-chloro-2-pentanone, which was converted to the Grignard reagent in the usual manner. The resulting intermediate was treated with trimethyl borate, and the resulting boron compound was esterified with (-)-pinanediol to yield the ethylene ketal of (-)-pinanediol 4-ketopentane-1-boronate, alternatively named (-)-pinanediol 4-(ethylenedioxy)pentane-1-boronate, bp 123°-124° C. (0.05 torr), [α]21 546 -17.03° (c 9.9%, chloroform), anal. C, H. B. This compound was treated according to the procedure of Example 1 to yield (-)-pinanediol (1R)-1-chloro-5-(ethylenedioxy)hexane-1-boronate, which was partially purified by concentration of the original reaction mixture, treatment with petroleum ether followed by saturated aqueous ammonium chloride, and concentration of the petroleum ether extract. The content of (1S) isomer was found to be less than 0.5% by 200 MHz NMR comparison with an epimeric mixture prepared from the corresponding ethylene glycol boronic ester (racemic) by transesterification with pinanediol. This crude product was treated with lithium benzyloxide to yield (-)-pinanediol (1S)-1-benzyloxy-5-(ethylenedioxy)-hexane-1-boronate, which was chromatographed on silica with 20% ethyl acetate in hexane. The yield was 94% (based on the 4-(ethylenedioxy)pentane-1-boronate), anal. C, H, B. By 200 MHz NMR analysis, the diastereomeric purity of this compound was approximately 98%. This compound was treated with dichloromethyllithium according to the procedure of Example 1 to yield (-)-pinanediol (1R,2R)-1-chloro-2-benzyloxy-6-(ethylenedioxy)-heptane-1-boronate, which was partially purified as described for the preceding α-chloro boronic ester in this example. This material was treated with ethylmagnesium bromide according to the usual method, as discussed in Example 4, but requiring 36 hr at 20°-25° C. for completion of the reaction, to yield (-)-pinanediol (3R,4R)-4-benzyloxy-8-(ethylenedioxy)-3-boronate; the latter being isolated by work up with petroleum ether and saturated ammonium chloride and chromatography on silica with 20% ethyl acetate in hexane. The yield of this compound was 82% (based on the 1-benzyloxy-5-(ethylenedioxy)-hexane-1-boronate), anal. C, H, B, [α]23 546 -2.09° (c 4.8%, chloroform). Oxidation of this compound with alkaline hydrogen peroxide followed by hydrolysis of the ethylene ketal with sulfuric acid-treated silica yielded (3R,4R)-4-benzyloxy-8-oxo-3-nonanol (79%); the NMR, infrared, and mass spectra of which were in agreement with values reported in Sherk et al., J. Org. Chem., Vol. 47, pp 932-935 (1982). However, the material prepared in this example had [α]23 589 -13.1° (c 4.3%, chloroform), and crystallized, from hexane, mp 30°-31° C., which removed all evidence of impurities from the 200 MHz NMR spectrum. Material which had not been recrystallized was converted to exo-brevicomin by the method disclosed in the above Sherk et al. article and had [α]23 589 +81.06° (c 1.4%, ether). Gas chromatographic analysis indicated the presence of 2% of the diastereomer, endo-brevicomin, and 200 MHz NMR analysis indicated 3% endo-brevicomin. The identification of exo-brevicomin as the principal component of the attractant pheromone of Dendroctonus brevicomis and the physical properties of exo-brevicomin and its endo isomer have been reported previously in Bellas et al., Tetrahedron, 25, pp 5149-5153 (1969) and Mori, Tetrahedron, 30, pp 4223-4227 (1974). (Bellas, Brownlee, and Silverstein).

1. additiontreated silica

ORD record

ord-a3c637c317104a48b78dcb9674d85f86

Source dataset

uspto-grants-1985_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04525309