4- Hydroxy-2-butenoates

Table 6 Effect of aryl substitution on enantioselectivity and regioselectivity in the AA of O-substituted 4-hydroxy-2-butenoates...

The reactivity and selectivity of cycloaddition can be considerably increased in intramolecular versions. The protocol was first demonstrated in the Diels-Alder reaction between anthrone 253416,417 and 4-hydroxy-2-butenoate mediated by phenylboronic acid (Equation (73)).418,419 Another method developed for the intramolecular cycloaddition is the synthesis of trienylboranes 256 by hydroboration of terminal alkynes (Equation (74)).419-422... 

Although reaction between 3-hydroxy-2-pyrone 315a and 4-hydroxy-2-butenoate 396a (R = H) does not occur in refluxing benzene, the cycloaddition in CeHe containing PhB(OH)2 followed by treatment with HOCH2C-... 

Narasaka and coworkers have reported the IMDA reaction of 3-hydroxy-2-pyrone 34 (Scheme 36) with 4-hydroxy-2-butenoate 144, which was temporarily tethered with phenylboronic acid, to provide a single cycloadduct 147 in 75% yield <91S1171>. This elegant strategy was further elaborated by Nicolaou and coworkers for the synthesis of 151 as the C-ring intermediate in their initial synthetic endeavors towards the total synthesis of taxol <92JCS(CC)1118 95JACS624>. 

Dimethyl-2(5H)-furanone (2,3-dimethyl-4-hydroxy-2-butenoic lactone) 3H-Furan-2-one... 

G.7) 2(5/f)-Furanone, but-2-eno-4-lactone, 2,5-dihydrofuran-2-one, 2-buten-4-olide, 2-butenoic acid, y-lactone, 4-hydroxy-2-butenoic acid, y-lactone, crotonolactone, isocrotonolactone [497-23-4]... 

A stereoselective synthesis of 5(5),6(7 ),15(5)-trihydroxy-20 4(7 ,9 ,l 1Z,13 ) from D-xylose using zinc-mediated deoxygenation of the 4-hydroxy-2-butenoic acid moiety and base- induced double elimination of 4,5-epoxy allyl chloride as key steps was reported (44). The enantiomers R)- and (5)-3-hydroxy-20 4(5Z,8Z,llZ,14Z) were synthesized from coupling of a chiral aldehyde intermediate with a Wittig salt, which were derived from 2-deoxy-D-ribose and arachidonic acid, respectively (45). 

The allylic HYCRAM derivative was subsequently modified by insertion of a standard amino acid between the aminomethyl resin and the hydroxy butenoic acid moiety. Using this allylic anchor, the resin-linked, glycosylated HIV peptide T-derivative 164 was synthesized by application of Fmoc amino protection and sidechain protection with lert-butyl groups. The lac-tosamine peptide T (165) could be released from the resin by application of the palladium(0)-catalyzed allyl-transfer reaction to V-methyl aniline as the allyl acceptor. 

To a stirred suspension of 2.3 mmol LDA in 20 mL of THF arc added at — 80 X under a nitrogen atmosphere 253 mg (1 mmol) of methyl 2-(2-hydroxy-2,6,6-trimethylbicyclo[3.1.1]hept-3-ylideneamino)propanoate and the mixture is stirred for a further 30 min. After the addition of 114 mg (1 mmol) of ethyl ( )-2-butenoate the mixture is stirred at — 80 °C until the reaction is complete (followed by TLC on silica gel). The mixture is poured into 70 mL of sat. aq NH4C1 and subsequently extracted three times with diethyl ether. The combined ether layers arc dried over Na2S04 and the solvent is evaporated. The crude adduct is purified by chromatography (silica gel. diethyl ether/hexane 66 34) yield 330 mg (90%). 

The enantioselective hydrogenation of a,fj- or / ,y-unsaturated acid derivatives and ester substrates including itaconic acids, acrylic acid derivatives, buteno-lides, and dehydrojasmonates, is a practical and efficient methodology for accessing, amongst others, chiral acids, chiral a-hydroxy acids, chiral lactones and chiral amides. These are of particular importance across the pharmaceutical and the flavors and fragrances industries. 

Kronberg L, Vartiainen T (1988) Ames mutagenicity and concentration of the strong mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone and of its geometric isomer E-2-chloro-3-(dichloromethyl)-4-oxo-butenoic acid in chlorine-treated tap waters. Mutat Res 206 177-182... 

Preparation of tetraalkylallenes by the pyrolysis of 2,2,4,4-tetraalkyl-3-hydroxy-3-butenoic acid /J-lactones at 150°-550°C [129]. 

Ethyl 3-cyclohexyl-3-hydroxy-4-trimethylsilylbutanoate (Structure 6) and ethyl 3-cyclohexyl-3-butenoate (Structure 7)... 

Indium-promoted addition of (Z)-2-(bromomethyl)-2-butenoate to ct-protected hydroxy aldehydes in water results in the selective formation of diastereomer 37 of the possible four stereoisomers 36-39 via the Felkin-Anh transition state (Scheme 40).170... 

Tosylmethyl isocyanide can react i.a. with fluoro- and perfluoroalkyl-substituted olefins, e.g., tert-butyl (E)-4,4,4-trifluoro-2-butenoate [9IJFC(53)61] and )8-perfluoroalkyl-substituted a,/3-unsaturated ketones (88CL1891) to provide 3-trifiuoromethylpyrroles. The latter are also accessible from isocyanoacetates and 3-nitro-2-hydroxy-l,l,l-trifluoroalkanes, which in situ are transformed into olefins on treatment with acetic anhy-dride/DBU (89BCJ3386) (Scheme 31). 

Dichloro-3-hydroxy E9a, 571 (2,3-Cl2—4-oxo — 2-butenoic Acid N2H2 or Semicarbazone)... 

The reaction of aryl azides with excess alkenes in the presence of trifluoroacetic acid proceeds by an analogous mechanism and afforded, after basic hydrolysis, /5-hydroxy amines together with byproducts. A diastereoselective reaction was observed only with cyclic and acyclic (Z/-alkenes, e.g., 12 and 1388. From methyl ( )-2-butenoate, A-phenylthreonine methyl ester was similarly prepared in 30% yield88. 

C6H10O3 ethyl 2-hydroxy-3-butenoate 91890-87-8 446.15 38.735 2 7987 C6H11BrO 2-(bromomethyl)tetrahydro-2H-pyran 34723-82-5 426.15 36.836 1.2... 

C10H1002 4-phenyl 3-butenoic acid 2243-53-0 575.15 51.149 1,2 19209 C10H10O4 3-hydroxy-4-methoxycinnamic acid, predominan 537-73-5 531.75 46.943 2... 

An alternative view has been expressed by Dittmer . The episulfone of dibenzoyl-stilbene is unusually stable. Pyrolysis at about 300 °C (25 torr) gave benzil (34, 31 %), diphenylacetylene (26, 31 %) and the lactone of 4-hydroxy-2,2,3,4-tetra-phenyl-3-butenoic acid (3, 7 %). 

A cleavage of carbon-oxygen bonds caused by amalgam reduction is found, for example, in the reduction of dihydroxyacetoxime to isopropylamine [121] and 2-hydroxy-4-phenyl-3-butenoic acid to 4-phenyl-3-butenoic acid [122]. These reactions are analogous to those discussed in Chapter 23. 

Figure 5.2.10. Cellulose pyrolysate obtained at 59CP C by Py-GC/MS. The separation was done on a Carbowax type column. 1 CO2, 2 acetaldehyde, 3 acetone, 4 2-butanone, 5 2,3-butandione, 6 toluene, 7 water, 8 cyclopentanone, 9 methylfuran, 10 3-hydroxy-2-butanone, 11 hydroxypropanone, 12 cyclopent-1-en-2-one, 13 2-methylcyclopentenone, 14 acetic acid, 15 acetic acid anhydride, 16 furancarboxaldehyde, 17 methylcyclopentenone, 18 dimethylcyclopentenone, 19 5-methylfurancarboxaldehyde, 20 2,3-dihydro-2-furanone, 21 furan-2-methanol, 22 3-methylfuran-2-one, 23 2(5H)-furanone, 24 hydroxycyclopentenone, 25 3,5-dimethylcyclopentan-1,2-dione, 26 2-hydroxy-3-methyl-2-cyclopenten-1-one, 27 2-hydroxy-3-ethyl-2-cyclopenten-1-one, 28 2,3-dimethyl-2-cyclopenten-1-one, 29 phenol, 30 dimethylphenol, 31 3 thyl-2,4(3H,5H)-furandione, 32 3-butenoic acid, 33 1,4 3,6-dianhydro-a-D-glucopyranose, 34 5-(hydroxymethyl)-furfural.

These terpene notes are supported by (Z)-3-hexenol, (E)-2-hexenal, (E)-2-hexenol with their fresh, green character. Gamma- and delta-lactones (4-decanolide, 5-decan-olide, 4-dodecanolide, 5-dodecanolide-(Z)-7-decen-5-olide) impart the sweet, creamy, buttery, peach and apricot character. 2,5-Dimethyl-4-hydroxy-furan-3(2H)-one and 2,5-dimethyl-4-methoxy-furan-3(2H)-one are responsible for the sweet creamy fruity body. A bouquet of esters imparts the overall fruity character (mainly esters of ethyl-, (Z)-3-hexenyl and butyl alcohol with acetic-, butanoic-, 2-butenoic, 3-hydroxybutanoic- and hexanoic acid). 

Studies on the bulk pyrolysis of polyhydroxybutyric acid from Bacilli and of bacterial polyalkanoates have shown the formation of 2,3-butenoic acid and 2,3-pentenoic acid (18) The presence of 2,3-butenoic acids and pentenoic acid in the pyrolysate of the particulate matter from sample 20C is interpreted as an indication of polyhydroxy-alkanoates in the sample. These mixed polyesters of hydroxy acids with 4, 5 and sometimes 6 carbon atoms are especially abundant in activated sludges (19). The occurrence of m/z 86 and 100 as abundant mass peaks in the spectra of the fluvial material and as very characteristic peaks in the discriminant function spectrum indicates that a significant amount of the mud fraction may consist of sewage debris. This impression was confirmed by identification of a number of other pyrolysis products in the data file. 

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