Epoxy Acid Research Articles

Acid etch resistance of automotive clearcoats. I: Laboratory test method development

This paper reports on the development of a laboratory test procedure for the evaluation of the environmental etch resistance of clearcoats. The test evaluates the bulk acid hydrolysis resistance of clearcoats by gravimetrically following material weight loss as a function of exposure time to a sulfuric acid solution, under conditions that simulate outdoor exposure. The bulk hydrolysis resistance of five production clearcoat technologies including acrylic melamine, acrylic melamine-silane, carbamate, acrylic urethane, and epoxy acid were evaluated. Results from the weight loss measurements were consistent with those anticipated based on the coating systems bulk chemistry and inherent hydrolysis resistance, for clearcoat systems processed under nominal processing conditions. The relative rankings from the laboratory test were found to correlate with field etch ratings. The test method is inexpensive, quantitative, and generates repeatable results that are not subject to environmental variations associated with current field etch testing.

A New Synthesis of Peptidyl Epoxysuccinates for Probing Cysteine Protease-Inhibitor P3/S3 Binding Interactions

A new synthesis of peptidyl epoxysuccinates has been developed involving the N-acylation of amino acid benzyl esters (12) with the tartrate ester derived epoxy acid 13 followed by depro- tection of the benzyl esters and acylation with amines 21-28. This synthesis is ideally suited for the rapid synthesis of peptidyl ep- oxysuccinate inhibitors of cysteine proteases, in order to probe se- lectivity issues concerning inhibitor/enzyme P 3/S3 binding interactions.

A Catalytic Asymmetric Synthesis ofN-Boc-beta-Methylphenylalanines.

An efficient, stereodivergent, and enantioselective synthesis of the syn and anti diastereomers of N-Boc-beta-methylphenylalanine has been developed. Starting from enantiomerically pure (2S,3S)-2,3-epoxy-3-phenyl-1-propanol, a three-step sequence, consisting of the oxidation of the primary alcohol up to the carboxyl stage, ring opening of the epoxy acid with Me(2)CuCNLi(2), and esterification of the resulting hydroxy acid with methyl iodide, leads to the hydroxy ester anti-10, which has been converted in a stereodivergent manner into both the (2S,3R) and the (2R,3R) diastereomers of N-Boc-beta-methylphenylalanine, syn-1 and anti-1, respectively. Activation of the secondary hydroxy group in anti-10 as a mesylate, followed by nucleophilic displacement with sodium azide, hydrogenolysis with simultaneous protection of the amino group, and saponification with LiOH, affords syn-1. The same reaction sequence applied to syn-10, obtained in turn by Mitsunobu reaction of anti-10 with p-nitrobenzoic acid followed by the hydrolysis of the resulting p-nitrobenzoate, leads to anti-1. Both products have been obtained with >/=99% enantiomeric excess.

Thermoplastic Elastomeric Blends of Nylon-6/Acrylate Rubber: Influence of Interaction on Mechanical and Dynamic Mechanical Thermal Properties

Abstract Nylon-6 and acrylate rubber (ACM) were melt blended in a Brabender Plasticorder at 220 °C and 40 rpm rotor speed. The reactive nature of the blend is reflected in the mixing torque behavior of the blends at different compositions. The solubility characteristics of the blends in formic acid solution gives an approximate idea of the amount of nylon-6 grafted onto ACM and vice-versa. A reaction mechanism is proposed based on the well known epoxy—amine and epoxy—acid reactions and is confirmed by infrared spectroscopic studies of the blends. The influence of interaction between the two polymers on the mechanical and the dynamic mechanical properties of the blends is analyzed in detail, and the results are interpreted on the basis of the formation of nylon—ACM graft copolymer at the interfaces. The dynamic mechanical thermal analysis (DMTA) reveals a two phase morphological structure, indicating incompatibility of the blend components. The grafting reaction results in dramatic increase in both the storage modulus and the Young's modulus of blends. The presence of grafted rubber chains is reflected in the secondary transition of the rubber loss peak at higher temperature. Also, a substantial improvement in the damping properties of the blends in the service temperature range (i.e., 25 to 175 °C) is revealed from the DMTA results. The dynamic vulcanization of the ACM phase during melt mixing improves the elongation at break values of the blends.

Biosynthesis of Dodecano‐4‐lactone in Ripening Fruits: Crucial Role of an Epoxide‐Hydrolase in Enantioselective Generation of Aroma Components of the Nectarine (Prunus persica var. nucipersica) and the Strawberry (Fragaria ananassa)

AbstractEarly steps in the biosynthesis of dedecano‐4‐lactone in ripening nectarines (Prunus persica var. nucipersica) and strawberries (Fragaria ananassa) were studied using cis‐9,10‐([18O]epoxy)heptadecanoic acid (5), instead of the natural C18‐precursor epoxystearic acid 1. In nectarines, an epoxide hydrolase catalyzed, in a highly regio‐ and enantioselective reaction, the attack of H2O at C(9) of epoxy acid 5 yielding preferentially (9R,10R)‐dihydroxyheptadecanoic acid 6a as an early intermediate and, after further metabolization, undecano‐4‐lactone 7a. In strawberries, the same transformation exhibited only a moderate regio‐ and enantioselectivity. Besides the previously established function of phytogenic epoxide hydrolases involved in generating oxygenated fatty‐acid derivatives, which are used in cutin monomer production and plant defence, a new rǒle for these enzymes now emerges in the enantioselective production of aroma components of ripening fruits. The cis‐9,10‐([18O]epoxy)heptadecanoic acid (≥ 98% 18O; 5) was obtained in good overall yield (68%) from isopropyl (9Z)‐heptadec‐9‐enoate using 18O2 gas in a free‐radical chain reaction in the presence of 2‐methylbutanal.

Substrate selectivity in esterification of less common fatty acids catalysed by lipases from different sources

Lipases from microorganisms (Candida cylindracea, Rhizopus arrhizus and Rhizomucor miehei), animal tissue (porcine pancreas) and a higher plant (rape, Brassica napus) have been evaluated as biocatalysts in the esterifications with n-butanol with regard to their substrate specificity towards fatty acids having a cis-4 unsaturation, e.g. docosahexaenoic (n-3 22:6), cis-6 unsaturation, e.g. petroselinic (n-12-18:1), γ-linolenic (n-6 18:3) and stearidonic (n-3 18:4), as well as cis-8 unsaturation, e.g. dihomo-γ-linolenic (n-6 20:3) acid, and fatty acids having unusual structures, e.g.cyclopentenyl (hydnocarpic and chaulmoogric), hydroxy (ricinoleic and 12-hydroxystearic) and epoxy (cis- and trans-9,10-epoxystearic) acids. A common feature of all the lipases tested is their ability to discriminate strongly against unsaturated fatty acids having a cis-4, cis-6 or a cis-8 unsaturation as substrates for esterification, whereas cyclopentenyl, hydrocy and epoxy acids are very well accepted as substrates. Esterification of the fatty acids of Hydnocarpus wightiana seed oil with n-butanol, catalysed by each of the above lipases, revealed that, as compared to the cyclopentenyl fatty acids having saturated alkyl chains, gorlic acid — a cyclopentenyl acid having a cis-6 unsaturation — is also strongly discriminated against as a substrate for esterification.

A Unified Strategy for the Stereocontrolled Construction of Structurally Unusual Sesquiterpene Lactones. Asymmetric Synthesis of Vulgarolide and Deoxocrispolide

The bicyclic ketone (+)-17b reacts with vinylmagnesium bromide from its exo face, thus enabling exploitation of the anionic oxy-Cope rearrangement and direct alkylation of the enolate so formed with ethyl iodoacetate to provide 24 in an efficient, stereocontrolled manner. Tricyclic lactone 26b, readily produced from 24, proved to be a common precursor to both synthetic targets. The construction of vulgarolide (9) proceeded by transforming the SEM group in 26b into a mesylate for the purpose of conversion to epoxy acid 39 in advance of oxidative cleavage of the double bond. This transformation resulted in direct conversion to 9 and its epimer 42. Central to the companion synthesis of deoxocrispolide (4) was the ability of 37 to undergo the Michael addition of methoxide ion and of 54 to experience regiocontrolled dehydration to bridgehead olefin 55 in a protocol that involves the smooth translocation of bridgehead unsaturation with concomitant functionalization as an allylic alcohol.

Intercropping Stokes Aster: Effect of Shade on Photosynthesis and Plant Morphology

Stokes aster [Stokesia laevis (Hill) E. Greene] is a potential new crop source of an epoxy acid but grows slowly and does not yield the first summer. It could be intercropped that year. To evaluate Stokes aster's response to intercrop shade, plants were grown under 1010 [high light (HL)], 320 [medium light (ML)], or 120 [low light (LL)] μmol m−2 s−1 photosynthetic photon flux density (PWD) for 50 d prior to measurements of photosynthetic rate, light compensation point, light saturation point, chlorophyll concentration, and morphology of whole plants. Near light saturation points, LL and ML plants had the highest net CO2 assimilation based on leaf area and ML plants were highest based on land area. High light plants were least efficient due to a vertical leaf orientation. As environment light intensity (LI) declined, plants had more chlorophyll per unit dry weight (DW), a higher chl b/chl a ratio, less leaf DW, less leaf area, and a lower root/shoot ratio. Light compensation points were 25, 55, and 185 μmol m−2 s−1 PPFD for LL, ML, and HL plants, respectively. Saturation points were between 400 and 800 μmol m−2 s−1 for LL plants and between 800 and 1500 μmol m−2 s−1 PPFD for ML and HL plants. In an intercrop, stokes aster should produce efficiently on a leaf area basis but less efficiently on a land area basis when grown under a LI of 120 μmol m−2 s−1 or less. Growth in full sun after the overstory crop is harvested would not be a problem for intercropped plants.

Total synthesis of natural (−)-vulgarolide. A concise stereocontrolled means for twofold distal oxaannulation of a cyclooctanone core

An anionic oxy-Cope rearrangement has been developed to produce enantiomerically pure keto ester 3, which was structurally modified to produce epoxy acid 2 whose ozonolysis led directly to a 1:1 mixture of (−)-vulgarolide and its anomer.

Oxygenated fatty acids of the seeds ofElaeagnus angustifolia

Among the oxidized lipids in the seed oil of the oliveElaeagnus angustifolia we have detected six epoxy acids and five hydroxy acids, of these 12-hydroxyoctadeca-8,10-dienone being new.

A short synthesis of the unusual amino acid of cyclosporine (4R)-4-[(E)-2-butenyl]-4,N-dimethyl-L-threonine (MeBmt)

MeBmt 1 was prepared in four steps from the optically pure (2Z, 4R) 4-methyloct-6-yn-2-en-1-ol 8, Z allylic alcohol containing an alkynyl group at the γ position. The two stereogenic centers C-2 and C-3 in the product were controlled using Sharpless' epoxidation and subsequent ring opening at C-2 of the epoxy acid 10 with methylamine.

Epoxidation ofLesquerella andLimnanthes (Meadowfoam) oils

AbstractLesquerella gordonii (Gray) Wats andLimnanthes alba Benth. (Meadowfoam) are species being studied as new and alternative crops. Triglyceride oil from lesquerella contains 55–60% of the uncommon 14‐hydroxy‐cis‐11‐eicosenoic acid. Meadowfoam oil has 95% uncommon acids, includingca. 60%cis‐5‐eicosenoic acid. Both oils are predominantly unsaturated (3% saturated acids), and have similar iodine values (90–91), from which oxirane values of 5.7% are possible for the fully epoxidized oils. Each oil was epoxidized withm‐chloro‐peroxybenzoic acid, and oxirane values were 5.0% (lesquerella) and 5.2% (meadowfoam). The epoxy acid composition of each product was examined by gas chromatography of the methyl esters, which showed that epoxidizedL. gordonii oil contained 55% 11,12‐epoxy‐14‐hydroxyeicosanoic acid, and epoxidized meadowfoam oil contained 63% 5,6‐epoxyeicosanoic acid, as expected for normal complete epoxidation. Mass spectrometry of trimethylsilyloxy derivatives of polyols, prepared from the epoxidized esters, confirmed the identity of the epoxidation products and the straightforward nature of the epoxidation process. Synthesis and characterization of these interesting epoxy oils and derivatives are discussed.

Thermal Decomposition of Fluorinated Dioxolane Carboxylates

AbstractSynthesis of fluorodioxole olefin monomers by thermal decomposition of fluorinated dioxolane carboxylic acid and the corresponding acyl chloride was explored. Complex product formation is observed, including acyl fluoride from Cl‐F exchange, the hydro‐dioxolane from proton abstraction, the cyclic ether ketone from dioxolane ring opening, and the epoxy acid fluoride from thermal rearrangement. The product distribution is strongly dependent upon reaction conditions. The main influential factors include the reaction temperature, the base used for the reaction, the presence or absence of solvent, and the counter ion associated with the intermediate salt. A mechanism is proposed to rationalize both the results and the product distribution. Methods to make authentic samples for product analysis are reported.

The study of natural epoxy oils and epoxidized vegetable oils by13C nuclear magnetic resonance spectroscopy

AbstractThe13C nuclear magnetic resonance spectra ofVernonia galamensis seed oil and of epoxidized palm super olein, soybean oil and linseed oil have been recorded and interpreted. The chemical shifts of the major signals are assigned and semi‐quantitative results are derived. The spectroscopic procedure provides a useful method of analyzing oils that contain epoxy acids. The epoxide function differs from a double bond in its influence on the chemical shifts of nearby carbon atoms.

Practical Synthesis of Optically Pure Methyl (2R,3S)-2,3-Epoxybutanoate via Microbial Asymmetric Reduction of α-Chloroacetoacetate

Asymmetric reduction of ethyl α-chloroacetoacetate (3) with Baker's yeast followed by treatment with sodium ethoxide afforded a mixture of ethyl (2R,3S)-(8) and (2S,3S)-2,3-epoxybutanoate (9) (8/9, 85: 15), which could be converted into the optically pure methyl (2R,3S)-2,3-epoxybutanoate (25) via one recrystallization of the brucine salt of the diastereomeric mixture of the corresponding epoxy acid

On the Specificity of a Fatty Acid Epoxygenase in Broad Bean (Vicia faba L.)

Seeds of broad bean (Vicia faba L.) contain a hydroperoxide-dependent fatty acid epoxygenase. Hydrogen peroxide served as an effective oxygen donor in the epoxygenase reaction. Fifteen unsaturated fatty acids were incubated with V. faba epoxygenase in the presence of hydrogen peroxide and the epoxy fatty acids produced were identified. Examination of the substrate specificity of the epoxygenase using a series of monounsaturated fatty acids demonstrated that (Z)-fatty acids were rapidly epoxidized into the corresponding cis-epoxy acids, whereas (E)-fatty acids were converted into their trans-epoxides at a very slow rate. In the series of (Z)-monoenoic acids, the double bond position as well as the chain length influenced the rate of epoxidation. The best substrates were found to be palmitoleic, oleic, and myristoleic acids. Steric analysis showed that most of the epoxy acids produced from monounsaturated fatty acids as well as from linoleic and alpha-linolenic acids had mainly the (R),(S) configuration. Exceptions were C(18) acids having the epoxide group located at C-12/13, in which cases the (S),(R) enantiomers dominated. 13(S)-Hydroxy-9(Z),11(E)-octadecadienoic acid incubated with epoxygenase afforded the epoxy alcohol 9(S),10(R)-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid as the major product. Smaller amounts of the diastereomeric epoxy alcohol 9(R),10(S)-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid as well as the alpha,beta-epoxy alcohol 11(R),12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoic acid were also obtained. The soluble fraction of homogenate of V. faba seeds contained an epoxide hydrolase activity that catalyzed the conversion of cis-9,10-epoxyoctadecanoic acid into threo-9,10-dihydroxyoctadecanoic acid.

Asymmetric synthesis of MeBma analog of C9 amino acid present in cyclosporine

MeBma 2, C 9 analog of MeBmt amino acid present in cyclosporine (immunosuppressive drug) is readily available in 5 steps (23% overall yield) from chiral aldehyde 7 by inermolecular opening at C-2 of chiral epoxy acid 10 with methylamine. The absolute configuration was initially introduced by means of Sharpless epoxidation of E chiral allylic alcohol 8.

Minor components ofLesquerella fendleri seed oil

Routine analysis of fatty ester fractions ofLesquerella fendleri oil suggested the presence of epoxy compounds and other minor components. By a combination of open silica column and high performance liquid chromatography (HPLC) fractionations of the methyl esters prepared from the oil, these constitutents were isolated and then characterized by thin‐layer chromatography‐mass spectrometry (GC‐MS—electron ionization, EI, and chemical ionization, CI) and nuclear magnetic resonance (NMR—1H and13C). Three epoxy acids, 15,16‐epoxy‐9,12‐octadecadienoic, 9,10‐epoxy‐12‐octadecenoic and 9,10‐epoxy‐octadecanoic, were found. Hydroxy acids present included a C‐22 homologue of lesquerolic acid (16‐hydroxy‐12‐docosenoic acid) and 14,15‐dihydroxy‐tricosanoic acid. Other minor ocmponents included four sterols, brassicasterol, campesterol, β‐sitosterol and stigmasterol, and a series of saturated and unsaturated fatty acids up to C30.

Pilot plant extraction of oil fromVernonia galamensis seed

Vernonia galamensis seed containing 40–42% oil and 30–34% epoxy acid, (cis‐12,13‐epoxy‐cis‐9‐octadecenoic) was processed to oil and meal. Seed conditioning, pressing and solvent extraction research were conducted in pilot facilities at the French Oil Mill Machinery Co. (Piqua, OH). The robust lipase system was successfully inactivated by treating 200 lb. batches ofV. galamensis seed in a cooker/conditioner at 195–200°F and >10% moisture. Conditioned seed was mechanically pressed and the press discharge cone setting was varied during operation from 1/32″ to 3/32″ to demonstrate the feasibility of both full pressing and prepressing. Prepressing successfully reduced oil level in the press cake to ca. 20%. Press cake was extracted with hexane in a 1.5‐ft3 batch‐type, four‐stage percolation unit with a 6″ square extraction cross section. Solvent extraction reduced oil level in the defatted meal to 1–2%. The defatted meal was desolventized and toasted. Excessive foaming of the vernonia oil extract made complete solvent stripping in the oil stripping unit difficult.

Epoxidation of α,β-Unsaturated Carboxylic Acids with Hydrogen Peroxide by Heteropoly Acids

Abstract The epoxidation of α,β-unsaturated carboxylic acids with 35%-H2O2 was carried out by the use of heteropoly acids (HPA) as catalyst. Among the HPA examined, CWP, prepared from 12-tungstophospholic acid (WPA) and cetylpyridinium chloride (CPC), was found to be the most efficient catalyst. The CWP-H2O2system provides an alternative method to prepare epoxy acids.