Synthesis of the three isomeric components of San Jose scale pheromone

The three isomeric components of the San Jose scale pheromone have been synthesized stereospecifically from a common intermediate β-keto ester.     

从月桂烯合成梨圆蚧性信息素

梨圆蚧是对果林危害较大的害虫。该虫的性信息素包括三个组分:3-亚甲基-7-甲基-7-辛烯-1-醇丙酸酯(1)、(2Z)-3,7-二甲基-2,7-辛二烯-1-醇丙酸酯(2)和(2E)-3,7-二甲基-2,7-辛二烯-1-醇丙酸酯(3)。本文介绍了通过对月桂烯进行结构改造来合成梨圆蚧性信息素,从月桂烯到1,总产率为19%。工业上从月桂烯制龋萑花醇和香叶醇,再将橙花醇和香叶醇转变为相应的氯烯醇后再还原、丙酰化即得2和3,其总产率分别为30%和28%。(以橙花醇和香叶醇计)。月桂烯可从β-蒎烯裂解而得。我国有丰富的蒎烯资源,所以开辟从月桂烯合成梨圆蚧性信息素的新途径具有重要的意义。     

梨圆蚧性信息素主要组成3,7-二甲基-2,7-辛二烯-1-醇丙酸酯的合成

Title compounds were prepared in 6 steps in 10% overall yield starting with Reformatskii reaction of Et acetobutyrate with Et bromoacetate.     

Synthesis of α-neryl and α-geranyl propionates — Components of the sex pheromone of San Jose scale

Summary An effective synthesis of -neryl and -geranyl propionates has been performed by the two-stage E/Z-C₅ homologization of 3-methylbut-3-en-1-yl iodide.N. D. Zelinskii Institute of Organic Chemistry, Moscow. All-Union Scientific-Research Institute of Biological Methods of Plant Protection, Kishinev. Institute of Chemistry, Bashkir Scientific Center, Urals Division, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 422–424, May–June, 1989.     

Vitamin-B12-Catalyzed C,C-Bond Formation. Synthesis of a california red scale pheromone

A Mixture of (3S,6R)- and (3R,6R)-3-methyl-6-(1-methylethenyl)dec-9-enyl acetate ( 1a and 1b , respectively)– 1a being a pheromone of the California red scale – is synthesized in 14 steps from (+)-(R)-limonene ( 4 ). The key step is the reductive vitamin- B ₁₂-catalyzed coupling of (R)-5-(2-iodoethyl)-6-mehtylhept-6-en-2-one ethylene acetal ( 8 ) and methyl crotonate ( 3 ).     

Synthesis of the AI component of the red san jose scale sex pheromone

Conclusions The racemic form of the AI component of the red San Jose scale pheromone and its analog were synthesized on the basis of available citronellol and geraniol derivatives.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1143–1146, May, 1989.     

Protonation, deprotonation, and protonation: conjugated photochemical reactions of ferrocenylazophenol

4-Ferrocenylazophenol (FAP) and 8-(4-ferrocenylazophenoxy)octanyl-1-bromide (FAOB) have been synthesized and their protonation and photochemical behavior have been investigated. FAP showed reversible protonation and deprotonation behavior in the presence of trifluoroacetic acid and potassium tert-butylate, respectively. FAP and FAOB exhibit high photoreactivity, which was induced through excitation of not only the pi-pi* band by UV light but also the d-pi* band by green light. The photoreaction of FAP and FAOB in ethanol or acetonitrile with a trace amount of water afforded phenylhydrazonocyclopentadiene (PHP) derivatives, indicating that hydrolysis of the photoexcited species occurs.     

Synthesis and characterization of a new conjugated polymer: Polytrifluoromethylacetylene

Polytrifluoromethylacetylene (PTFMA) was synthesized from trifluoromethylacetylene (TFMA) using a PdCl₂/DMF catalyst solution or the anionic initiator n-butyl lithium. Although PdCl₂ proved to be an effective catalyst for the polymerization of TFMA, long reaction times and poor yields made characterization of the resultant polymer difficult. The use of n-butyl lithium, on the other hand, resulted in high yields of PTFMA in relatively short reaction times. The results of thermal analysis and the effects of n- and p-type doping on the electrical conductivity of the polymer are discussed.     

Oxa-di-pi-methane photochemical rearrangement of quinuclidinones. Synthesis of pyrrolizidinones

[reaction: see text] The oxa-di-pi-methane (ODPM) photochemical rearrangement, a triplet-sensitized sigmatropic 1,2-acyl shift of beta,gamma-enones, was successful utilizing methyl and heptyl 1-aza-3-carboalkoxybicyclo[2.2.2]oct-2-en-5-ones (quinuclidinones) as the photoprecursors. The cyclopropane of the heptyl ester tricyclic photoproduct could be opened with lithium dimethylcuprate or via hydrogenolysis to produce the corresponding pyrrolizidinone skeletons.     

Synthesis of macrocyclic esters by catalytic cyclization

Macrocyclic esters were synthesized in good yield through catalytic cyclization by metal salts of glycol monosuccinates. The procedure is an improvement over catalytic depolymerization for the preparation of cyclic compounds, as developed by Carothers.     

Synthesis of amino acid esters by papain

A wide range of N-Boc-amino add esters were synthesized from N-Boc-amino acids and alcohol using papain as catalyst. Suitable biphasic reaction mixtures were found for most amino acids to achieve high yield of ester synthesis. With N-Boc-L-aspartic and glutamic adds only the a carboxyl group is esterified, without racemisation.     

Preparation of phosphinic acids: Michael additions of phosphonous acids/esters to conjugated systems.

A very mild and facile method for the preparation of phosphinic acids via Michael addition of phosphonous acids as well as esters, through an intermediate silyl alkyl phosphonite, to activated conjugated systems is described.     

Synthesis of (R)-mellein by a partially reducing iterative polyketide synthase

Mellein and the related 3,4-dihydroisocoumarins are a family of natural products with interesting biological properties. The mechanisms of dihydroisocoumarin biosynthesis remain largely speculative today. Here we report the synthesis of mellein by a partially reducing iterative polyketide synthase (PR-PKS) as a pentaketide product. Remarkably, despite the head-to-tail homology shared with several fungal and bacterial PR-PKSs, the mellein synthase exhibits a distinct keto reduction pattern in the synthesis of the pentaketide. We present evidence to show that the ketoreductase (KR) domain alone is able to recognize and differentiate the polyketide intermediates, which provides a mechanistic explanation for the programmed keto reduction in these PR-PKSs.     

Organoboron compounds Communication 7. Action of phosphorus pentachloride on areneboronic esters. Synthesis of arenechloroboronic esters

Summary When benzeneboronic and o-tolueneboronic esters were treated with phosphorus pentachloride, benzenechloroboronic and o-toluenechloroboronic esters were obtained, these being the first representatives of a new type of boron compounds.