Synthesis Of Side Chain Research Articles

A Trifunctional Catalyst for One‐Pot Synthesis of Chiral Diols via Heck Coupling—N‐Oxidation—Asymmetric Dihydroxylation: Application for the Synthesis of Diltiazem and Taxol Side Chain.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The synthesis and mesogenic properties of side chain polymethacrylates with terminal branched groups

The synthesis is described of six polymethacrylates attached through oxytetramethylene and oxyhexamethylene spacers to an azobenzene moiety consisting of branched terminal iso-butoxy, iso-amyloxy and n-amyloxy groups. The monomers show a nematic mesophase while their polymers show an additional higher order smectic C phase. The effects of the terminal branched alkoxy group and the spacers on mesomorphic properties are discussed. The phase characteristics, thermal stabilities and molecular masses of the polymers were investigated by DSC, XRD, TGA and GPC. The polymers were also characterized by UV-vis, IR and NMR spectroscopy.

Regiospecifically Deuterated (‐)‐Δ9‐Tetrahydrocannabivarins.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A trifunctional catalyst for one-pot synthesis of chiral diols via Heck coupling-N-oxidation-asymmetric dihydroxylation: application for the synthesis of diltiazem and taxol side chain.

A heterogeneous bifunctional catalyst composed of OsO4(2-)-WO4(2-) and a trifunctional catalyst comprising PdCl4(2-)-OsO4(2-)-WO4(2-), designed and prepared by an ion-exchange technique using layered double hydroxides (LDH) as an ion-exchanger and their homogeneous bifunctional analogue, K2OsO4-Na2WO4 and trifunctional analogue, Na2PdCl4-K2OsO4-Na2WO4, devised for the first time are evaluated for the synthesis of chiral vicinal diols. These bifunctional and trifunctional catalysts perform asymmetric dihydroxylation-N-oxidation and Heck-asymmetric dihydroxylation-N-oxidation, respectively, in the presence of Sharpless chiral ligand, (DHQD)2PHAL in a single pot using H2O2 as a terminal oxidant to provide N-methylmorpholine oxide (NMO) in situ by the oxidation of N-methylmorpholine (NMM). The heterogeneous bifunctional catalyst supported on LDH (LDH-OsW) displays superior activity to afford diols with higher yields over the other heterogeneous catalysts developed by the ion exchange on quaternary ammonium salts covalently bound to resin (resin-OsW) and silica (silica-OsW) or homogeneous catalysts in the achiral dihydroxylation reactions. The LDH-OsW and its homogeneous analogue are found to be very efficient in performing a simultaneous asymmetric dihydroxylation (AD)-N-oxidation of a wide and varied range of aromatic, cyclic, and mono, di-, and trisubstituted olefins to obtain chiral vicinal diols with higher yields and ee's using H2O2. Further, the use of OsO4(2-)-WO4(2-) catalysts as such or in the supported form offers a simplified procedure for catalyst recycling, which shows consistent activity for a number of cycles. In this process, Os(VI) is recycled to Os(VIII) by a coupled electron transfer-mediator (ETM) system based on NMO-WO4(2-) using H2O2, leading to a mild and selective electron transfer. The one-pot biomimic synthesis of chiral diols is mediated by a recyclable trifunctional heterogeneous catalyst (LDH-PdOsW) consisting of active palladium, tungsten, and osmium species embedded in a single matrix. This protocol, which provides prochiral olefins and NMO in situ by Heck coupling and N-oxidation of NMM, respectively, required for the AD, unfolds a low cost process. We extended the present method to the one-pot synthesis of trisubstituted chiral vicinal diols with moderate to excellent ee's by AD of trisubstituted olefins that are obtained by in situ Heck arylation of disubstituted olefins. The heterogeneous trifunctional catalysts offers chiral diols with unprecedented ee's and excellent yields in the AD of prochiral cinnamates, which are obtained in situ from acrylates and halobenzenes for the first time. The new variants such as LDH support and Et3N*HX inherently composed in the heterogeneous multicomponent system and slow addition of H2O2 facilitates the hydrolysis of osmium monogylcolate ester to subdue the formation of bisglycolate ester to achieve higher ee's. Without resorting to recrystallization, the chiral diols of cinnamates thus synthesized with 99% ee's and devoid of osmium contamination are directly put to use in the synthesis of diltiazem and Taxol side chain with an overall improved yield to demonstrate the synthetic utility of the trifunctional heterogeneous catalyst. The high binding ability of the heterogeneous osmium catalyst enables the use of equimolar ratio of ligand to osmium to give excellent ee's in AD in contrast to the homogeneous osmium system in which the excess molar quantities of the expensive chiral ligand to osmium are invariably used. Further, the XRD, FT-IR, UV-vis DRS, and XPS studies indicate the retention of the coordination geometries of the specific divalent anions anchored to LDH matrix in their monomeric form during the ion exchange and after the reaction.

A Practical and Stereoselective Synthesis of Taxol Side Chain

A practical and efficient synthesis of taxol C-13 side chain from cheap and easily available starting material is described.

Lipase-Catalyzed Kinetic Resolution of 4-(N-Boc-amino)-1-alken-3-ols

A wide range of 4-(N-Boc-amino)-1-alken-3-ols were efficiently resolved by lipase-catalyzed kinetic resolution. This procedure has been successfully applied to the highly enantioselective synthesis of the taxol side chain.

Synthesis of side chain specifically deuterated (−)‐Δ9‐tetrahydrocannabinols

Abstract(−)‐Δ9‐Tetrahydrocannabinols specifically deuterated at the n‐pentyl side chain were prepared using the corresponding resorcinols as key intermediates. To obtain the deuterated resorcinols we developed conditions under which no deuterium scrambling or loss was observed. The methodology allows for the preparative scale synthesis of deuterated resorcinols and corresponding (−)‐Δ9‐tetrahydrocannabinols. Copyright © 2002 John Wiley & Sons, Ltd.

Synthesis and biological activities of new side chain and backbone cyclic bradykinin analogues.

A series of conformationally constrained cyclic analogues of the peptide hormone bradykinin (BK, Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) was synthesized to check different turned structures proposed for the bioactive conformation of BK agonists and antagonists. Cycles differing in the size and direction of the lactam bridge were performed at the C- and N-terminal sequences of the molecule. Glutamic acid and lysine were introduced into the native BK sequence at different positions for cyclization through their side chains. Backbone cyclic analogues were synthesized by incorporation of N-carboxy alkylated and N-amino alkylated amino acids into the peptide chain. Although the coupling of Fmoc-glycine to the N-alkylated phenylalanine derivatives was effected with DIC/HOAt in SPPS, the dipeptide building units with more bulky amino acids were pre-built in solution. For backbone cyclization at the C-terminus an alternative building unit with an acylated reduced peptide bond was preformed in solution. Both types of building units were handled in the SPPS in the same manner as amino acids. The agonistic and antagonistic activities of the cyclic BK analogues were determined in rat uterus (RUT) and guinea-pig ileum (GPI) assays. Additionally, the potentiation of the BK-induced effects was examined. Among the series of cyclic BK agonists only compound 3 with backbone cyclization between positions 2 and 5 shows a significant agonistic activity on RUT. To study the influence of intramolecular ring closure we used an antagonistic analogue with weak activity, [D-Phe7]-BK. Side chain as well as backbone cyclization in the N-terminus of [D-Phe7]-BK resulted in analogues with moderate antagonistic activity on RUT. Also, compound 18 in which a lactam bridge between positions 6 and 9 was achieved via an acylated reduced peptide bond has moderate antagonistic activity on RUT. These results support the hypothesis of turn structures in both parts of the molecule as a requirement for BK antagonism. Certain active and inactive agonists and antagonists are able to potentiate the bradykinin-induced contraction of guinea-pig ileum.

Identification and synthesis of some contaminants present in 4-methoxyamphetamine (PMA) prepared by the Leuckart method

The clandestine synthesis of ring and side chain modified phenylisopropylamines continues to be a major source of these drugs of abuse. One method used for the synthesis of the amphetamine and related compounds involves the treatment of the appropriate ketone with formamide or ammonium formate followed by acid hydrolysis of intermediate N-formyl derivative. In this paper the synthesis of 4-methoxyamphetamine (PMA, 1) by the Leuckart method is investigated. The identification by means of gas chromatography–mass spectrometry (GC–MS) of methoxy derivative of N-(β-phenylisopropyl)benzaldimine 9, methoxy derivative of N-(β-phenylisopropyl)benzyl methyl ketimine 5, 1-(4-methoxyphenyl)-N-(4-methoxybenzyl)-2-propanamine 10, (RR/SS) and (RS) 1-(4-methoxyphenyl)-N-[2-(4-methoxyphenyl)-1-methylethyl]-2-propanamine 6a–6c, (RR/SS) and (RS)-1-(4-methoxyphenyl)-N-methyl-N-[2-(4-methoxyphenyl)-1-methylethyl]-2-propanamine 7a–7c, (RR/SS) and (RS)-1-(4-methoxyphenyl)-N-formyl-N-[2-(4-methoxyphenyl)-1-methylethyl]-2-propanamine 8a–8c in crude PMA, are reported. The identity of these compounds was confirmed by independent synthesis of reference compounds. The NMR, MS, IR data, stereochemistry and some chromatographic properties of synthesized compounds are discussed. Finally, the results of the GC–MS analysis of illicitly prepared tablets, containing PMA 1 and 4-methoxymethamphetamine (PMMA, 2), are outlined. The presence of 4-methoxydimethylamphetamine 11, 4-methoxyethylamphetamine 12, and 4-hydroxymethamphetamine 13 are reported in these tablets. The identity of 2, 11, and 12 was confirmed by their independent synthesis.

Synthesis of side chain truncated 3"-aldehyde, 3"-carboxylic acid, and 1"-aldehyde from nodulisporic acid A.

An efficient synthesis of the truncated 3"-aldehyde (3) from nodulisporic acid A (1) under mild conditions is described. Further oxidation of 3 to 3"-carboxylic acid (4) and its subsequent oxidative degradation produced 1"-aldehyde (5). These new derivatives are versatile intermediates for the preparation of new, side chain modified derivatives of nodulisporic acid A. [reaction: see text]

Regiospecifically deuterated (−)-Δ9-tetrahydrocannabivarins

Deuterated (−)-Δ9-tetrahydrocannabivarins (Δ9-THCVs) can be used as markers for confirming the illicit use of marijuana. Here, we first describe an efficient synthesis of side chain deuterated Δ9-THCVs from the respective 5-propylresorcinols specifically deuterated at the side chain. Our approach involved the development of optimal, high yield methods for the introduction of deuterium at the C-3′ and C-2′ position of the side chain.

Epithelial cell contact-induced alterations in Salmonella enterica serovar Typhi lipopolysaccharide are critical for bacterial internalization.

The invasion of Pseudomonas aeruginosa and Salmonella enterica serovar Typhi into epithelial cells depends on the cystic fibrosis transmembrane conductance regulator (CFTR) protein as an epithelial receptor. In the case of P. aeruginosa, the bacterial ligand for CFTR is the outer core oligosaccharide portion of the lipopolysaccharide (LPS). To determine whether serovar Typhi LPS is also a bacterial ligand mediating internalization, we used both P. aeruginosa and serovar Typhi LPS as a competitive inhibitor of serovar Typhi invasion into the epithelial cell line T84. P. aeruginosa LPS containing a complete core efficiently inhibited serovar Typhi invasion. However, neither killed wild-type Typhi cells nor purified LPS were effective inhibitors. LPS from mutant Typhi strains defective in O side-chain synthesis, but with an apparently normal core, was capable of inhibiting invasion, but LPS obtained from a deeper rough mutant strain with alterations in fast-migrating core oligosaccharide failed to inhibit invasion. Lastly, exposure of wild-type serovar Typhi to T84 cultures before heat killing resulted in a structural alteration in its LPS that allowed the heat-killed cells to inhibit invasion of wild-type serovar Typhi. These data indicate that the serovar Typhi LPS core, like the P. aeruginosa LPS core, is a ligand mediating internalization of bacteria by epithelial cells, and that exposure of this ligand on wild-type Typhi is induced by the bacteria's interaction with host cells.

Stereocontrolled synthesis of contignasterol's side chain

The four models of the contignasterol's side chains ( 2– 5 ) have been stereospecifically prepared. The key reaction in the synthesis is a dimethylaluminum chloride-mediated ‘ene’ reaction between the steroid derivative 6 and the pseudo-enantiomeric aldehydes 7 and 8 .

Synthesis of side chain truncated apicularen A

The potent cytostatic agent apicularen A belongs to a growing class of macrocyclic salicylates with unique biological properties. Herein, we present a short enantioselective synthesis of side chain truncated apicularen A.

Synthesis of side chain modified apicidin derivatives: potent mechanism-based histone deacetylase inhibitors

An efficient degradation of apicidin's ketone-containing side chain to two common intermediates (the C7-aldehyde and the C8-methyl ester) is described. From these intermediates, a series of potent mechanism-based histone deacetylase inhibitors was prepared to facilitate biochemical studies.

Recent Advances in the Medicinal Chemistry of Taxoids with Novel P-Amino Acid Side Chains

Amino acids have been recognized as an important class of compounds in the design and synthesis of potential pharmaceutical drugs and also for the study of enzymatic reaction mechanisms. Among the -amino acid family, isoserines (a-hydroxy- -amino acids) are probably the most important members because many of them are potent enzyme inhibitors and they also serve as essential building blocks for biologically and medicinally important molecules such as Taxol®. Taxol® (paclitaxel) and Taxotere®(docetaxel) are currently considered to be the most important drugs in cancer chemotherapy. This review describes recent advances in the chemistry of isoserines and taxoid anticancer agents at the biomedical interface including (i) the development of highly efficient method for the synthesis of isoserine side chains of taxoids and (ii) the synthesis and structure-activity relationship (SAR) study of taxoids featuring discovery and development of the "second generation" taxoid anticancer agents that possess exceptional activities against drug-resistant cancer cells.

New side chain liquid crystalline polymers: synthesis and thermal properties of side chain polyacrylates having segmented spacers

In order to acquire high mobility of a mesogenic group, we propose a new type of side chain liquid crystal polymer having segmented spacers, consisting of binary moieties of an oligo(ethylene oxide) segment and analkylene segment. Six kinds of polyacrylates having segmented spacers consisting of different lengths of an oligo(ethylene oxide) and an alkylene, and having 4'-cyanobiphenyl as a mesogenic group have been synthesized, and their thermal properties investigated. Some of these polyacrylates exhibit a mesophase and show an extremely low glass transition temperature compared with LC polyacrylates having ordinary alkylene spacers.

ChemInform Abstract: A Facile Synthesis of Cephem Side Chains by Palladium Catalyzed Cross‐Coupling of 3‐Substituted‐Δ3‐Cephems with Dialkylzinc or Vinyltributyltin.

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A facile synthesis of cephem side chains by palladium catalyzed cross-coupling of 3-substituted-Δ 3-cephems with dialkylzinc or vinyltributyltin

Synthesis of 3-vinyl- and 3-alkyl-Δ 3-cephems was performed in a regioselective manner by palladium acetate catalyzed reaction of 3-sulfonato- or 3-bromo-Δ 3-cephems with dialkylzinc or vinyltributyltin. A new access to 3-alkyl-Δ 3-cephems is opened, starting from the allenyl compound 10.

Syntheses of carbon-11 labeled piperidine esters as potential in vivo substrates for acetylcholinesterase

A series of carbon-11 labeled N-methylpiperidinyl esters were prepared as potential in vivo substrates for acetylcholinesterase (AChE). Target compounds were designed based on the structure of N-[ 11C]methylpiperidin-4-yl propionate, an ester currently used to measure AChE enzymatic activity in the human brain, to examine the structure–activity relationship for in vivo enzymatic hydrolysis. Changes in steric bulk and in the ester order (“reverse” esters) were made. Addition of methyl groups was made to both the acid side chain (synthesis of N-[ 11C]methylmethylpiperidin-4-yl isobutyrate) and to the piperidine ring (syntheses of N-[ 11C]methyl-4-methylpiperidin-4-yl propionate, N-[ 11C]methyl-4-methylpiperidin-4-yl acetate, and N-[ 11C]methyl-3-methylpiperidin-4-yl propionate). Alterations of the order of the ester heteroatoms was accomplished through syntheses of the N-[ 11C]methyl-2,3- and 4-piperidinecarboxylic acid ethyl esters. Finally, an additional piperidine-based ester ( N-[ 11C]methylpiperidin-2-yl)methyl propionate was also prepared. All carbon-11-labeled esters were prepared by N-[ 11C]methylation reactions, using the desmethyl precursors and no-carrier-added [ 11C]methyltriflate, and were obtained in decay-corrected yields (not optimized) of 10–40% and high specific activities.