Showing papers on "Diazomethane published in 1998"

Enantioselective Synthesis of (−)-Pumiliotoxin C from a Chiral Amino Ester and an Acetylenic Sulfone that Acts as an Alkene Dipole Equivalent

Abstract: A new synthesis of the naturally occurring (−)-enantiomer of the dendrobatid alkaloid pumiliotoxin C (1) was achieved by the conjugate addition of methyl (−)-cis-2-amino-trans-6-methylcyclohexanecarboxylate (3) to 1-(p-toluenesulfonyl)-1-pentyne (4), followed by intramolecular acylation to afford (4aS,5R,8aR)-4a,5,6,7,8,8a-hexahydro-5-methyl-2-propyl-3-(p-toluenesulfonyl)-4-quinolinone (2). The acetylenic sulfone thus acts as the synthetic equivalent of an alkene dipole species. The required enantiopure amino ester 3 was obtained by an approach based on pig liver esterase (PLE)-mediated hydrolysis. Thus, the (−)- and (+)-enantiomers of racemic dimethyl trans-3-methylcyclohexane-cis,cis-1,2-dicarboxylate (6) afforded the corresponding half-esters 7 and 8, respectively, when treated with PLE. The desired half-ester 7 was recovered intact after selective conversion of the free carboxylic acid group of the byproduct 8 into its benzyl ester. Half-ester 7 was converted into enantiopure (−)-6 with diazomethane, ...

Stereoselective synthesis of biologically active tetronic acids

Abstract: (4R)-3-Amino-4-trimethylsilyloxy-2-alkenoates (R)-3, obtained from O-trimethylsilyl protected optically active cyanohydrins (R)-1 via the Blaise reaction, are hydrolyzed under mildly acidic conditions to give optically active tetronic acids (R)-4 without racemization. From the follow-up reactions of (R)-4 investigated, only methylation with diazomethane afforded the biologically active tetronic acid derivative (R)-5a without racemization whereas acylation and reductive alkylation, respectively, resulted in partial racemization or failed on the whole.

Analyzing HAAs and ketoacids without diazomethane

Abstract: Currently available methods for analyzing haloacetic acids (HAAs) and ketoacids in water generally require the use of diazomethane for sample derivatization. This article proposes methods based on a less toxic, alternative methylated agent. The reagent in both cases is acidic methanol. Side-by-side comparison of the proposed method for HAA analysis and method 6251B showed no significant difference. These two methods were also found to give similar method detection limits and spike recoveries. The new O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylarnine (PFBHA)-acidic methanol derivatization analytical method for two ketoacids-glyoxylic acid and pyruvic acid-was found to be comparable to the method using PFBHA-diazomethane. Additional study is needed to improve methylation efficiency for ketomalonic acid. Work is also needed to further test the proposed HAA method with monochloroacetic acid and brominated haloacetic acids.

Ring Expansion and Contraction of a Two-Carbon Bridged Spiropentane

Abstract: The reactions of tricyclo[4.1.0.01,3]heptan-4-one (5) and two related systems with diazomethane and m-CPBA were examined in order to determine the relative reactivity and migratory aptitudes for the three compounds. The reactions of 5 with diazomethane and m-CPBA yielded new derivatives of the tricyclo[5.1.0.01,3]octane ring system that showed that migration of cyclopropylcarbinyl is favored over cyclopropyl migration in this system. Photolysis of 5-diazotricyclo[4.1.0.01,3]heptan-4-one (23) in methanol and dimethylamine did not lead to ring contraction to the tricyclo[3.1.0.01,3]hexane ring system, but an interesting product was derived from an unusual rearrangement process in the photolysis in dimethylamine. Matrix photolysis of 23 at 15 K gave a decrease in the diazo band at 2085 cm-1 and the appearance of a new band at 2117 cm-1, which is a normal position expected for a small-ring ketene such as cyclopropylketene. Thus, matrix photolysis appears to have yielded a derivative of the previously unknown ...

Addition of diazomethane to 3 and 4-nitrophthalodinitriles

Abstract: The reaction of two nitrophthalodinitriles with diazomethane is described. If the nitro group is at position 3, only one of the two nitrile functions reacts giving three isomeric N-methyl 1,2,3-triazoles. In contrast, if the nitro group is at position 4, both nitriles react, each producing a 2-N-methyl 1,2,3-triazole. The reactivity was accounted for in terms of electronic densities, which were determined for several nitrile compounds. Interestingly, for 4-nitrophthalodinitrile, original methylation of the aromatic ring at position 5 was also observed. I n t r o d u c t i o n In a previous study (1) on the addition of diazomethane to different nitriles, we showed that the addition reaction requires the presence of an electroattractive group. We describe here the reactivity of the 3and 4-nitrophthalodinitriles 2 and 3, and compare it with the unreactivity of phthalodinitrile 1. The nitrophthalodinitriles were stirred during several days with a solution of diazomethane in diethyl ether. The reaction was followed by thin-layer chromatography. Resu l t s In the case of 3-nitrophthalodinitrile 2, three N-methyl 1,2,3-triazoles 4, 5 and fLderived from the cyano group at position 2 were isolated (cf figure 1).

Theoretical Study of the Mechanism of the Addition of Diazomethane to Ethylene and Formaldehyde. Comparison of Conventional ab Initio and Density Functional Methods

Abstract: The 1,3-dipolar cycloaddition reactions of diazomethane with ethylene and formaldehyde as well as the nitrogen elimination reactions from the cycloadducts have been studied using density functional...

Controlling π-Facial Diastereoselectivity in the 1,3-Dipolar Cycloadditions of Diazomethane to Chiral Pentenoates and Furanones: Enantioselective Stereodivergent Syntheses of Cyclopropane Hydroxy Acids and Didehydro Amino Acids

Abstract: The title compounds have been synthesized in both enantiomeric forms and in good overall yields by using d-glyceraldehyde as the single chiral precursor. The efficiency and usefulness of the synthe...

Syntheses of Phospholipids Containing 2-Nitrobenzyl Ester Moieties at the Terminals of Alkyl Chains and Properties of Photodegradable Liposomes from the Lipids

Abstract: Phospholipid 1a bearing 2-nitrobenzyl ester moieties as a photocleavable group at the terminal of alkyl chains was synthesized from the corresponding terminal carboxy-bearing phospholipid 2 by the reaction with 2-nitrophenyl-substituted diazomethane. Phospholipid, 1b bearing α-methyl-2-nitrobenzyl group, 1c bearing 4,5-dimethoxy-2-nitrobenzyl group, and 1d bearing α-methyl-4,5-dimethoxy-2-nitrobenzyl group were similarly synthesized by the use of the respective diazo compounds. The order of photolysis rates of 2-nitrobenzyl ester linkage of phospholipids by ultrahigh-pressure mercury lamp is 1b ≥ 1d > 1a > 1c. Liposomes of 1a—1d containing calcein in the inner aqueous layer were prepared by vortexing, sonication, and gel-filtration. UV irradiation resulted in fast release of the entrapped fluorescence dye. The order of release rates : 1b ≥ 1d > 1c > 1a is consistent with that of photolysis rates except for 1c, which has poor retention of the dye.

Gas Chromatographic Analysis of Tall Oil Fractionation Products After Methylation with N,N-Dimethylformamide Dimethylacetal

Abstract: Tall oil fractionation products such as tall oil fatty acids, distilled tall oil, and tall oil rosin are routinely analyzed by gas chromatography (GC) after derivatization with diazomethane or esterification with methanol using boron trifluoride as a catalyst. An alternative derivatizing reagent, N,N-dimethylformamide dimethylacetal, has been investigated for the preparation of methyl esters of fatty acids and resin acids in tall oil fractionation products prior to GC analysis. This reagent provides a safe, rapid, and reproducible means of derivatization that eliminates the need to isolate the methyl esters from the derivatization reaction mixture.

Large scale batch process for diazomethane

Abstract: Diazomethane is prepared in a batch process on a scale of at least 50 gram-moles per batch, from an N-methyl-N-nitroso amine in an organic solvent and an inorganic base in an aqueous solution by the use of a phase transfer catalyst and by controlling the choice of solvent, reagent concentrations, addition rate and reaction temperature to cause codistillation of the product and the organic solvent in such a manner that the concentration of diazomethane in both liquid and vapor phases are controlled within limits that will prevent detonation of the diazomethane.

Assay of salicylic acid and related compounds in plant cell cultures by capillary GC

Abstract: A capillary gas chromatographic (GC) method for the assay of salicylic acid (1) and related compounds in plant cell cultures is described. The gas chromatograms were validated qualitatively by means of GC-mass spectrometry. The detection limits of 1 (50 ng) and 2,3-dihydroxybenzoic acid (2; 125 ng), obtained in the GC split injection mode, could be lowered 25- to 50-fold by using the splitless mode. Derivatization of these compounds with diazomethane gave the methyl esters as major derivatization products in yields of 98% and 94%, respectively. The extraction recoveries of 1 and 2 from lyophilized Catharanthus roseuscells were more than 95%, using o-anisic acid as internal standard, and tetrahydrofuran was found to be a suitable extraction solvent. © 1998 John Wiley & Sons, Ltd.

The reaction of 3-acetyl coumarin with alkyl phosphites and phosphonium ylides

Abstract: Dialkyl phosphites reacted with 3-acetyl coumarin (1) at 100°C for about 5 h to give the phosphonates having structure 4. Methylation of compounds 4 with ethereal solution of diazomethane gave the respective methyl ethers 5. Treatment of 1 with trimethyl phosphite afforded a mixture of the phosphonates 5a and 4a whereas with triethyl phosphite gave a mixture of compounds 6 and 4b. The reaction of phosphonium ylides 8a-d with 1 in boiling toluene led to the formation of two isomers (E)-allylic (9) and (Z)-allylic (10). The structural assignments of all new compounds are based on IR and NMR (H, 13C) spectra.

Quinazolinones As Potential Anti-Inflammatory Agents

Abstract: 2-Methyl-3-arylidenamino-4 (3H)-quinazolinones (la-le) on cyclocondensation with thiolactic acid and diazomethane are converted into thiazolidinyl quinazolinones (IIa-IIe) and triazolidinyl quinazolinones (IIIa-IIIe) respectively. Their structures have been delineated by IR, 1HNMR and mass spectroscopy. The compounds were evaluated for anti-inflammatory activity.

Development of a solid-phase extraction and derivatization method for polar carboxylic acids from aqueous extracts of inorganic multi-component incineration residues

Abstract: A rapid and reliable GC/MS (EI and CI) method was developed for the identification of short-chain mono- and dicarboxylic acids in complex and strongly alkaline residues of municipal waste incineration. Such residues contain organic carboxylic acids in the mg/kg to μg/kg range, which may contribute to the mobilization of heavy metals. However, the alkalinity and the high salt loads of the matrix were found to be a serious problem in the analysis of short chain acids. Extraction with water, solid phase extraction, and derivatization were studied under these conditions. Solid-phase extraction with polymeric sorbents and derivatization with diazomethane can be combined in a reproducible manner to yield a robust and simple method which can be applied for screening unknown solids due to its wide applicability and the well identifiable methyl esters. Absolute recovery rates varied between 20 and 85% depending on the individual acids.

Chemical amplification type resist composition

Abstract: PROBLEM TO BE SOLVED: To improve contrast and to ensure high resolution, a high rate of a residual film and high sensitivity by using a diazomethane compd having acid-dissociable groups as an acid generating agent SOLUTION: This resist compsn contains a coating film forming component whose alkali solubility is varied by the action of an acid an acid generating agent made of a diazomethane compd represented by the formula, wherein each of R and R is a carbocyclic or heterocyclic group ring-substd by an acid-dissociable group, R and R may be different from each other and the acid-dissociable group is, eg tert alkyloxycarbonyl such as tert butoxycarbonyl or tert amyioxycarbonyl, tert alkyloxycarbonylalkyl such as tert butoxycarbonylmethyl, tert alkyl such as tert butyl, alkoxyalkyl such as ethoxyethyl or methoxypropyl or tetrahydropyranyl

Synthesis of Optically Active Spiro‐β‐Lactams by Cycloadditions to α‐Alkylidene‐β‐Lactams.

Abstract: New optically active α-methylene-β-lactam 18 and the α-ethylidene-β-lactams 11-E and 11-Z were synthesized and submitted to 1,3-dipolar cycloadditions with diazomethane, 4-methoxybenzonitrile oxide, and diphenylnitrone as well as to epoxidation by dimethyldioxirane. All cycloadditions proceed with complete regioselectivity giving products 20 – 25 in an anti-fashion with respect to the substituent at the C-4-position of the starting β-lactam in diastereomeric ratios of about 80:20. Pure optically active compounds could be obtained in almost all cases after chromatography. Unambiguous structure elucidation could be achieved by X-ray crystal analysis and NOE investigations.

Production of 2-amino-3-carboxy-1,4-naphthoquinone

Abstract: PROBLEM TO BE SOLVED: To enable to obtain the subject compound having an activity for stimulating the proliferation of bifidobacterium in a large amount in a high yield and at a low cost by successively subjecting 1,4-dihydroxynaphthoic acid to a methyl esterification reaction, an oxidation reaction, an amination reaction and a deesterification reaction. SOLUTION: This method for producing 2-amino-3-carboxy-1,4-naphthoquinone comprises methyl-esterifying 1,4-dihydroxynaphthoic acid with diazomethane, oxidizing the obtained methyl 1,4-dihydroxynaphthoate with silver oxide in the presence of a dehydrating agent such as anhydrous magnesium sulfate, aminating the obtained 2-carboxymethyl-1,4-naphthoquinone with sodium azide and subsequently deesterifying the obtained 2-amino-3-carboxymethyl-1,4- naphthoquinone with boron tribromide. The method enables to obtain the objective compound in a far larger amount and at a far lower cost than those by a conventional method comprising culturing a bacterium belonging to the genus Propionibacterium.