2.8- Dimethyl-l,7-dioxaspiro

Recordings from Staphylininae [115] include 3-methylbutanal, the corresponding alcohol, and its acetate, various ketones such as 4-methyl-3-hexanone, 4-methyl-3-heptanone, 5-methyl-3-hexanone (and the corresponding alcohol), 2-heptanone, 6-methyl-2-heptanone, 6-methyl-5-hepten-2-one as well as methyl-cyclopentene and methylfuran. In addition, the secretions of Ontholestes murinus contain the spiroacetals (2S,6R,8S)-2,8-dimethyl-l,7-dioxaspiro[5,5]-... 

Enantiomers of 2,7-dimethyl-l,6-dioxaspiro[4.5]decane 28 Enantiomers of 2-Ethyl-7-methyl-l,6-dioxaspiro[4.5]decane 29 Enantiomers of 2,8-dimethyl-l,7-dioxaspiro[5.5]undecane 30 5 - Methylh eptan - 2 -ol (Z)-Non-3-en-l-ol 3,7-Dimethyloctan- l-ol Benzaldehyde 2-Phenylethanol Phenylacetonitrile Isobutyl benzoate Isopentyl benzoate Hexadecanoic acid 17-Hydroxyan drost-4-en-3-one (2)-Octadec-9-enoic acid... 

Polybia occidentalis W-VG Alarm (2S,6J ,8S)-2,8-Dimethyl-l,7-dioxaspiro-[5.5] undecane 142 [188]... 

Mercuriocyclization has also been utilized in order to obtain spiroketals from hemiketals. Thus, treatment of l,10-undecadien-6-one (11) with mercury(II) acetate in water/tetrahydrofuran affords, with total regioselectivity, 2,8-bis[(chloromercurio)mcthyl]-l,7-dioxaspiro[5.5]undccanc as a diastereomeric mixture. The diastereomeric ratio was not reported but depends on the reaction time, owing to the reversibility of oxymercuration-cyclization steps. Reductive removal of mercury by sodium borohydride under phase-transfer conditions gives a good yield of 2,8-dimethyl-l,7-dioxaspiro[5.5]undecane (12) as a diastereomeric mixture101,102. 

Male palaearctic bees (Andrena wilkella) in Sweden produce 2,8-dimethyl-l,7-dioxaspiro[5.5]undecane (88, Figure 4.34) as their pheromone. Its (25, 6R,83 )-isomer is pheromonally active, while the opposite enantiomer (2R,6S,8R)-88 is inactive.63 There are six stereoisomers of 2,8-dimethyl-1,7-dioxaspiro[5.5]undecane (88), three as shown in Figure 4.34 and their opposite enantiomers. Due to the oxygen-anomeric effect, (2S,6R,8S)-88 and its opposite enantiomer are the stable isomers. 

The synthesis of (2 5, 6R, 8 S)-2,8-dimethyl-l,7-dioxaspiro[5,5]undecane (868), one of the spiroacetal components of the pheromone isolated from the olive fruit fly, hinges on a dialkylation of tolylmethyl isocyanide with bromide 866. The bromide is obtained from 845b by sequential reduction of the olefin and ester followed by conversion of the resulting alcohol to bromide. Acidic hydrolysis of dialkylated product 867 provides the pheromone 868 directly... 

Thus, starting from ethyl (5)-p-hydroxybut5rrate, pheromones of diverse structural types, such as (5)-sulcatol [26], femilactone II [27], (25,6i )-2-methyl-l,7-dioxaspiro[5.6]-dodecane [28], (25,6/ ,S5)-2,8-dimethyl-l,7-dioxaspiro[5.5]undecane [29], (2R,5S)-2-methyl-5-hexanolide [31], and (2S,SjR)-8-methyl-2-decanol propanoate [32], have been synthesized. Methyl (5)-P-hydroxybutyrate has also been used for the synthesis of (25,35,75)-3,7-dimethylpentadecan-2-ol [33]. In these syntheses, the configurations at the... 

Lactones have been converted to (hydroxyalkyljcyclopropyl phenyl ketones on reaction with phenylmagnesium bromide and phenyllithium. Reductive dimerization of ethyl cyclo-propanecarboxylate with sodium gave l,2-dicyclopropylethane-l,2-dione in 69% yield when thionyl chloride treatment was carried out prior to hydrolytic workup, and to dicyclopropyl ketone in 74% yield, when workup included sodium bromate treatment. A related reaction occurred during thermolysis of 6,6-dimethyl-5,7-dioxaspiro[2.5]octane-4,8-dione to give dispiro[2.1.2.1. ]octane-4,8-dione. ... 

Et3N (40 pL, 0.29 mmol) and imidazole (20 mg, 0.29 mmol) were added to a solution of (4R,8R)-8-ethyl-4-hydroxy-l,7-dioxaspiro[5.5]undec-2-ene (38 mg, 0.29 mmol) in DMF (2 mL) and the resulting solution was stirred for 5 min. (Bromomethyl)dimethyl-silyl chloride (40 pL, 0.29 mmol) was then added and the reaction was stirred for 3 h. The reaction was quenched by the addition of NaHC03 solution (satd) and diluted with Et20. The organic layer was washed with brine, dried (MgS04) and then concentrated in vacuo. Purification of the residue by flash column chromatography (EtOAc/hexane, 1 1) provided the silyl ether 139 as a labile, colorless oil (62 mg, 93%). 

The volatile component of the mandibular secretion of Andrena haemorrhoa F. contains 2,7-dimethyl-l,6-dioxaspiro[4.6]undecane. All four thermodynamically stable stereoisomers of the Spiro acetal pheromone have been prepared using the two enantiomers of ethyl lactate (which supplies the 2-methyl substituent via butyrolactone 51) and the two enantiomers of 3-hydroxybutanoate (which supplies the 7-methyl via iodide 52). Scheme 8 shows the synthesis of the (2S, 5S, 7/ )-isomer 55. The overall yield in the sequence is 9%, and the purity of the final product is 97% [18]. 

A wide range of 3,3-disubstituted cyclopropenes, e.g. the dimethyl and diphenyl derivatives, as well as spiro[2.4]hept-l-ene or 6,6-dimethyl-4,8-dioxaspiro[2.5]oct-l-ene, can thus be reacted with a variety of mono- and disubstituted alkynes. Usually, the chemoselectivity of this cy-clocotrimerization reaction is remarkably high. The norcaradiene derivatives initially obtained are in equilibrium with the valence tautomeric cycloheptatrienes. The equilibrium ratio of the valence tautomers is strongly dependent on the position and kind of substituents, especially those in the 7-position of the newly formed norcaradienes and cycloheptatrienes. When one or two phenyl groups are present in this position, only norcaradiene products can be detected by and NMR spectroscopy at room temperature, whereas in the case of methyl substituents, both valence tautomers are formed in almost equal amounts. When cyclic alkynes, such as cyclooctyne, are employed in the reaction, only norcaradienes are formed regardless of the substituents present in the cyclopropene cosubstrate. ... 

Sodium benzenethiolate reacted with 6,6-dimethyl-2-vinyl-5,7-dioxaspiro[2.5]octane-4,8-dione (16) to give the 1,5-addition product only. When ethyl trani-6-(l-heptenyl)-2-oxo-bicyclo[3.1.0]heptane-l-carboxylate (18, R = Et) was treated with potassium benzenethiolate it was converted stereospecifically to the corresponding trawj -cyclopentanone derivative 19 (R = Et) with a defined configuration at the a-carbon atom of the side chain. This reaction proved to be useful for the stereoselective synthesis of prostaglandins. ... 

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