Molecular structure of vinylphosphine derivatives. Electron diffraction study of Cl2P−CH=CR2 (R=H,Me)

Internal rotation about the P?C bonds in the Cl₂PCH=CH₂ and Cl₂PCH=CMe₂ molecules is diseussed. It is shown that the cis (with eclipsed C=C bonds and lone electron pair of the phosphorus atom) and eclipsed conformers of the Cl₂PCH=CH₂ molecule are in equilibrium. The geometrical parameters and conformation compositions are refined. The content of the cis conformer is 40%. The Cl?P?C=C torsion angles are ±128.5° for the cis conformer and ?29.6 and ?132.6° for the eclipsed conformer. The Cl₂PCH=CMe₂ molecule occurs only in the cis form. For Cl₂PCH=CMe₂, the geometrical parameters are as follows: bond lengths C?H=1.124(11), C=C=1.322(8), P?C=1.789(3), and P?Cl=2.042(2) Å; bong angles (deg) C?P?Cl=99.1(4), Cl?P?Cl=99.6(6), C=C?CH₃=120.1 and 125.7, and P?C=C=122.3(9); torsion angles Cl?P?C=C=±129.3(3).     

Pheromones of insects and their analogs. XX. Methyl-branched pheromones based on 4-methyltetrahydropyran.

A synthesis is proposed of 4,8-dimethyldecanal (VIII) — a pheromone of the flour beetlesTribolium confusum andT. castaneum. By heating 71.2 g of 4-methyltetrahydropyran (I), 83.2 g of AcBr and 1.57 g of ZnCl₂ (45°C), then 120°C, 2 h), 1-acetoxy-5-bromo-3-methylpentane (II) was obtained. The hydrolysis of 19.8 g of (II) (MeOH-H₂O, TsOH, 20°C, 15 h) gave 5-bromo-3-methylpentan-1-ol (III). From 18.1 g of (III) and 38.9 ml of 2,3-dihydropyran (Et₂O, TsOH, 20°C, 20 h) was obtained the 2-THPL ester of (III), (IV), which was converted into 3-methyloct-7-en-1-ol (V) by the treatment of the corresponding Grignard reagent with allyl bromide (THF, CuI-bi-2-pyridyl, 2°C, 4 h, Ar). The interaction of 1.42 g of (V) with Et₃Al (hexane, 20°C, Cp₂ZrCl₂, Ar) gave 3,7-dimethylnonan-1-ol (VI), boiling which with 48% HBr in the presence of concentrated H₂SO₄ gave 1-bromo-3,7-dimethylnonane (VII) which was then converted into the desired (VIII) by the reaction of the corresponding Grignard reagent with DMFA (0–2°C, 1 h; 20°C, 2 h; Ar). The characteristics of the compounds — yield (%), n_D (°C): (I), 79, 1.4340 (22); (III) 89, 1.4660 (23); (IV), 82, 1.4739 (23); (V), 85, —; (VI), 90, 1.4483 (20); (VII), 88, 1.4409 (22); (VIII), 88, 1.4589 (22). Details of the IR and PMR spectra of compounds (II)–(VII) are given.Institute of Chemistry, Bashkir Scientific Center, Urals Branch, USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 272–276, March–April, 1989.     

The neomycin biosynthetic gene cluster of Streptomyces fradiae NCIMB 8233: characterisation of an aminotransferase involved in the formation of 2-deoxystreptamine

The biosynthetic gene cluster of the 2-deoxystreptamine (DOS)-containing aminoglycoside antibiotic neomycin has been cloned for the first time by screening of a cosmid library of Streptomyces fradiae NCIMB 8233. Sequence analysis has identified 21 putative open reading frames (ORFs) in the neomycin gene cluster (neo) with significant protein sequence similarity to gene products involved in the biosynthesis of other DOS-containing aminoglycosides, namely butirosin (btr), gentamycin (gnt), tobramycin (tbm) and kanamycin (kan). Located at the 5'-end of the neo gene cluster is the previously-characterised neomycin phosphotransferase gene (apH). Three genes unique to the neo and btr clusters have been revealed by comparison of the neo cluster to btr, gnt, tbm and kan clusters. This suggests that these three genes may be involved in the transfer of a ribose moiety to the DOS ring during the antibiotic biosynthesis. The product of the neo-6 gene is characterised here as the L-glutamine : 2-deoxy-scyllo-inosose aminotransferase responsible for the first transamination in DOS biosynthesis, which supports the assignment of the gene cluster.     

Synthesis of methyl-branched low-molecularmass insect bioregulators from the products of the acid decyclization of 4-methyltetrahydropyran

This review generalizes work on the chemoselective synthesis of racemic methyl-branched insect pheromones and the juvenoid hydroprene from 1,5-bifunctional 3-methylpentanes produced by the acid opening of the ring of 4-methyltetrahydropyran.Institute of Organic Chemistry, Ufa Scientific Center, Russian Academy of Sciences. Scientific-Research Institute of Fine Organic Synthesis Academy of Sciences of the Republic of Bashkortostan, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 170–177, March–April, 1977.     

Conformational analysis of 5,6-dihydropyrimidine and its derivatives

The equilibrium geometry and inversion barriers of 5,6-dihydropyrimidine, 6,7-dihydroazolopyrimidines with node nitrogen atoms and their alkyl (Me, Et, Prⁱ, Bu^t) and phenyl derivatives were calculated using a molecular mechanics approach. Annelation with azole cycles and the introduction of substituents have a slight effect on the equilibrium conformation of the dihydrocycle (distorted sofa). Alkyl substutuents at saturated carbons have an essentially equatorial orientation in 5,6-dihydropyridimine derivatives and are axial in the annelated analogs. On the other hand, the equatorial conformers are more stable in phenyl derivatives of dihydroazolopyrimidines. Factors determining the relative stability of conformers were analyzed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 487–491, March, 1995.     

Disproportionation of 6,8-Dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-Dioxides under Conditions of Acid Hydrolysis and Acetylation

Acid hydrolysis and acetylation of 6,8-dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-dioxides have been studied. 6,8-Dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-dioxides disproportionate to 4,4'-sulfonyldiiminobis(1,3-dialkylimidazolidin-2-ones) and sulfamide when treated with acid at pH 1 or with acetyl chloride. The kinetics of the disproportionation have been studied.     

The physicochemical properties of aqueous mixtures of cationic-anionic surfactants: I. The effect of chain length symmetry

The solution behaviors of equimolar mixtures of cationic-anionic surfactants have been studied by means of the dynamic light scattering technique and surface tension measurements. The surface activity and the micellization properties are different for systems of different hydrophobic chain length symmetry. For systems of lower symmetry (e.g., C₆H₁₃NC₅H₅Br-C₁₂H₂₅SO₄Na mixture), the surface tension at cmc (γ_cmc) is rather high (above 30 mN m⁻¹) and the mixtures form genuinely homogeneous micellar solutions above the cmc. For the systems of high symmetry (e.g., C₈H₁₇NC₅H₅Br-C₈H₁₇SO₄Na mixture), γ_cmc is very low (about 24 mN m⁻¹, near the value of pure hydrocarbon) and in the apparently homogeneous and clear mixtures slightly above cmc, the aggregates grow slowly and eventually form small droplets; as the concentration is further increased, all these solutions become turbid. We have proposed a new concept of conformation energy of aggregates to account for all these phenomena. Mixtures of octyltriethylammonium bromide and sodium octylsulfate form clear homogeneous micellar solutions in keeping with predictions based upon this concept.     

Indole derivatives

A method for the introduction of a 3-indolyl group in compounds with an active methylene group was developed. The corresponding 3-indolyl diketones were obtained by condensation of 1-acetyl-3-indolinone with dimedone, 4-hydroxycoumarin, 1,2-diphenyl-3,5-pyrazolinedione, and barbituric and thiobarbituric acids and subsequent alkaline hydrolysis of the condensation products. The existence of cyclic six-membered 3-indolyl diketones in the enol form and of cyclic five-membered 3-indoly diketones in the keto form was shown by IR and UV spectroscopy. Depending on the conditions, (1-acetyl-3-indolyl)cyanoacetamide, 1,3-bis(1-acetyl-3-indolyl)-1,3,3-tricyano-2-amino-1-propene, and 1-acetyl-3-indolylmalononitrile are obtained in the condensation of 1-acetyl-3-indolinone with malononitrile. 1-Acetyl-3-indolylmalononitrile exists in equilibrium with the keteneimine form and in protic solvents is converted to 3-cyano-8-acetylpyrrolo[2,3-b]indole by intramolecular cyclization.See [1] for communication CX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 360–368, March, 1977.     

Hydroxylamine derivatives

The condensation of urethane and ethyl acetohydroximate with 2-chloromethyl-1-methylbenzimidazole has given, respectively, N-ethoxycarbonyl-O-(1-methylbenzimidazol-2-ylmethyl)hydroxylamine and ethyl N-(1-methylbenzimidazol-2-ylmethoxy)acetimidate. Acid hydrolysis of the latter has given O-(1-methylbenzimidazol-2-ylmethyl)hydroxylamine. The reactions of its derivatives with HCl have been studied, and it has been shown that 1-methylbenzimidazole-2-aldehyde O-(1-methylbenzimidazole-2-methyl)oxime is formed. The structure of the latter has been shown by an analysis of its PMR spectra.For part II, see ¦1¦.