Stereospecific synthesis of a key synthon for faranal — The trail pheromone of the antMonomorium pharaonis

An effective scheme is proposed for the synthesis of the methoxymethyl derivative of racemic (erythro)-5-iodo-3,4-dimethylpentan-1-ol (a for obtaining faranal) from methyl (erythro)-3,4,5-trimethylhex-5-enoate — the product of the diastereospecific 1,4-addition of 2,3,-dimethylallylmanganese chloride to methyl crotonate. Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 459–463, May–June, 1993.     

MS/MS in structural analysis of an oviposition-deterring pheromone

A recently characterized oviposition-deterring pheromone (ODP, structure 1) of the European cherry fruit fly was used as a test case for probing the potential of tandem mass spectrometry (MS/MS) in structure elucidation as a stand-alone technique. The glycolipid-taurinate 1 was subjected to MS/MS analyses under a variety of conditions with and without preceding chemical degradation. Acidic methanolysis of 1 and subsequent in-batch derivatization (trideuterioacetylation) yielded methyl 2,3,4,6-tetrakis-O-trideuterioacetyl-glucopyranoside (2), methyl 8,15-bis-trideuterioacetoxy-palmitate (3), and taurine (4) as suitable target compounds for direct mixture analysis.Low energy collision induced dissociation (CID) on selected precursor ions (MS/MS on [M + H – CH₃OH]⁺ and [M + H]⁺ produced by fast atom bombardment (FAB)) allowed direct identification of 2 and 4, respectively, by comparison with appropriate reference ions. In the case of 3, low energy CID (desorption chemical ionization (DCI) instead of FAB, MS/MS on [M + H]⁺) permitted deduction of gross molecular structure, but failed to provide positional detail. In sharp contrast,high energy CID of trideuterioacetylated intact 1 (FAB-MS/MS on [M – H]^– ions of la) clearly revealed a linear 8,15-hydroxylated palmitic acid backbone. Less certain was assignment of 15-O-glucosylation by this approach.     

Tandem mass spectrometry in the structural analysis of an oviposition-deterring pheromone

The potential of tandem mass Spectrometry (MS/MS) as a stand-alone technique in the structural analyses of an oviposition-deterring pheromone (ODP, 1) is reviewed. Two facets of the salt-like glycolipid structure of 1 were of major interest in this context: the substitution pattern of the lipid backbone (15-glucosyioxy-8-hydroxypalmitate) and, more specifically, the configurational identity of the sugar portion (glucopyra nose). Throughout this study, trideuterioacetyl derivatives of ODP (1 → pentakis(trideuterioacetyl)-ODP la) and the reference substrates were used. Probing of the sugar moiety by fast atom bombardment (FAB) and both low- and high-energy collision-induced dissociation (CID) of B₂-type sugar ions surprisingly failed as a single exception within a larger number of glycosidic substrates subjected to this approach. However, electrospray ionization (ESI) of la with the formation of the sugar ions in the gas phase by ‘first-stage’ CID before mass selection circumvented this difficulty and provided an unambiguous and sensitive probe for sugar stereochemistry. When studying the ODP molecule as a whole, FAB-generated M-like ions such as [M ? H]^?, [M + Na]⁺ and [M ? H + 2Na]⁺ were subjected to high-energy CID using a four-sector tandem mass spectrometer. Analyses of simple model substrates such as the 12-trideuterioacetoxystearate anion facilitated the interpretation of the distinct charge-remote fragmentation (CRF) behaviour of la. Whereas all M-like species provided complete records of the lipid portion of la and its oxygenation pattern, only the sodiated cations allowed reliable location of the individual substituents. In these latter species complementary series of ‘sequence ions’ were observed that incorporated either the taurine or the sugar terminus and thus reflected CRF for both alternatives of terminal charge fixation.     

Formal synthesis of (±)-camptothecin via tricyclic lactone as key synthon

Formal synthesis of (±)-camptothecin via CDE tricyclic lactone employing tandem Michael addition, Dieckmann condensation and addition-elimination reaction as key steps starting from glycinate is described.     

A study of the sex pheromone ofTortrix viridana

cis-Tetradec-ll-en-l-ol acetate has been isolated from an extract of the sex pheromone of the green oak tortrixTortrix viridana L., and has proved to be attractive under sexual conditions for the males of this species.All-Union Scientific-Research Institute of Biological Methods of Plant Protection, Kishinev, Moldles Moldavian Forestry Scientific-Production Amalgamation, Bendery, and All-Union Scientific-Research Institute of Chemical Means of Plant Protection, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 645–649, September–October, 1981.     

A new synthon for the synthesis of aminoinositol derivatives

The regio- and stereoselective synthesis of a new synthon, trans-3,8-dioxatricyclo[3.2.1.0^2,4]octane-6,7-diamine, from 7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate is reported. Transformation of the acid functionalities to acyl azides followed by Curtius rearrangement gave the corresponding trans-diisocyanate, which was reacted with HCl to produce a trans-diamino compound that is a potentially important synthon for the versatile synthesis of aminocyclitols.     

Synthetic strategies to epoxydiynes and a key synthon of the neocarzinostatin chromophore

We present herein our recent efforts towards the synthesis of epoxydiynes which represent an unusual structural feature of the neocarzinostatin chromophore. A number of different routes to these epoxydiynes have been explored with varying success. Ultimately a concise and convergent approach was developed, which involved the addition of an allenyl zinc bromide to propargylic ketones/aldehydes followed by epoxide formation. This new protocol enabled us to synthesise a fully elaborated epoxydiyne which will find application for our studies towards the total synthesis of the NCS chromophore.     

10-甲基-PGD2的合成子的合成

PGD2的合成子(9)的合成是以2-甲基环戊1,3-二酮(1)为原料, 经烯醇醚化、烯丙基化、酸去保护、羰基的锂铝氢还原、臭氧化、氧化、甲酰化获得.     

Asymmetric synthesis of a sex pheromone (3S,5R,6S)-3,5-dimethyl-6-isopropyl-3,4,5,6-tetrahydropyran-2-one

An Oppolzer anti-aldol approach for the synthesis of the sex pheromone (3S,5R,6S)-3,5-dimethyl-6-isopropyl-3,4,5,6-tetrahydropyran-2-one is reported.     

Effective asymmetric synthesis of the key chiral building blocks of 20(S)- and 20(R)-camptothecins

Abstract  

An effective diastereoselective synthesis of (S)-N,N-diethyl-2-formyl-2-(methoxymethoxy)butanamide and (S)-2-formyl-2-(methoxymethoxy)butanoic acid ethyl ester, which are two key chiral building blocks for the synthesis of 20(S)-camptothecins, has been developed by employing an asymmetric bromolactonization using (R)-proline. The (R) compounds were also synthesized to obtain 20(R)-camptothecin.     

2-Carbomethoxycyclopentenone as a synthon. synthesis of sarkomycin

The first regiospecific synthesis of sarkomycin (II), a compound active against ascites-type tumors, is reported. Treatment of 2-carbomythoxycyclopentenone (I) with Et₂AlCN generated the carbon skeleton; aelective functional group manipulations then gave the keto lactone X and the protected hydroxy acid XI; and mild acid treatment of these led to sarkomycin.     

A new one-pot synthesis of all E-retinoic acid via a new enaminodiester synthon

A ‘one-pot’ synthesis of allE-retinoic acid from a new enaminodiester was described. The enaminodiester was easily produced from methyl isopropylidenemalonate and DMF-DMA.     

Botcinolide/botcinin: asymmetric synthesis of the key fragments

The asymmetric synthesis of key fragments of the phytotoxic toxins botcinolide/botcinin is reported. The synthesis of 1 and 1a are based on a convergent route via esterification and alkene metathesis of fragments A, B or C, B, which were obtained by Evans aldol condensation and stereoselective crotylation, respectively.     

Stereoselective synthesis of the Paulownia bagworm sex pheromone

According to our retrosynthesis, the main chain of the target molecule could be constructed using a C5 + C7 + C5 strategy. The key induction reaction afforded chiral methyl group moieties using different Evans templates with different configurations. Li_2 Cu Cl_4was effectively employed in the Csp~3 Csp~3 coupling protocol. The target molecular was obtained in a 12.6% overall yield with nine steps in the longest linear route.     

Regioselective synthesis of virazole using benzyl cyanoformate as a synthon

An antiviral nucleoside or virazole was synthesized efficiently and regioselectively starting with benzyl cyanoformate.     

(R)-4-menthen-3-one in the synthesis of (3S)-methylundecand (2S)-methyldec-1-ylbromides, key synthons for (S,S,S)-diprionylacetate

New capabilities for the synthetic use of (R)-4-menthen-3-one were demonstrated using as examples (3S)-methylundec- and (2S)-methyldec-1-ylbromides, key synthons for (S,S,S)-diprionylacetate (sex pheromone of pine sawflies of genera Diprion and Neodiprion).     

Stereospecific synthesis of the sex pheromone of the passionvine mealybug, Planococcus minor

A short and completely stereospecific synthesis of (E)-2-isopropyl-5-methyl-2,4-hexadienyl acetate, the very recently identified sex pheromone of the passionvine mealybug Planococcus minor, is described. In the key step, CuI-catalyzed anti-addition of a Grignard reagent to a propargyllic alcohol intermediate gave the required trisubstituted alkene with 100% regio- and stereospecificity. The stereochemical purity of the pheromone is critically important because the (Z)-isomer is a powerful behavioral antagonist.     

Novel synthesis of Planococcus citri pheromone

An effective method was proposed for synthesizing (+)-cis-1R-acetoxymethyl-3-isopropenyl-2,2-dimethylcyclobutane, a pheromone of the citrus mealybug, based on ozonolysis of verbenone that led in one step to the key synthon 1R,3S-3-acetyl-2,2-dimethylcyclobutanecarboxylic acid. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 179–180, March–April, 2006.     

Coordination networks constructed with supramolecular synthon RX–CCAgn (n = 4, 5; RX = halophenyl)

Eight new silver(I) double salts: AgL¹·2AgCF₃COO (1), AgL¹·3AgNO₃ (2), 2AgL²·5AgCF₃COO·2CH₃CN·H₂O (3), 4AgL³·6AgCF₃COO·5CH₃CN (4), 4AgL⁴·6AgCF₃COO·5CH₃CN (5), 2AgL⁵·4AgCF₃COO·NC(CH₂)₄CN (6), 2AgL⁵·4AgCF₃COO·2CH₃CN (7) and AgL⁶·2CF₂(CF₂COOAg)₂·2CH₃CN (8) (L¹ = 4-iodophenylethynide; L² = 3,4-dichlorophenylethynide; L³ = 3-chlorophenylethynide; L⁴ = 3-bromophenylethynide; L⁵ = 2-chlorophenylethynide; L⁶ = 2-fluorophenylethynide) have been synthesised and characterized by X-ray crystallography. All compounds contain the silver–halophenylethynide supramolecular synthon R_X−CCAg_n (n = 4, 5). In particular, the three-dimensional supramolecular structures in 1 and 2 are stabilized by strong AgI interactions, while that in 3 is consolidated by both AgCl and van der Waals type FCl interactions. In isomorphous compounds 4 and 5, the presence of respective FCl or FBr contact contributes to the stability of the network. The silver aggregates in 6, 7 and 8 are stabilized by AgCl or AgF interactions between the ortho-halo substituent and the Ag_n basket.