Dehydro ester

The principal constituents of rosin (qv) are abietic and related acids. Tall oil (qv) is a mixture of unsaturated fatty and aHcycHc acids of the abietic family. Refined tall oil may be high in rosin acids or unsaturated acids, depending on the refining process. Ethoxylates of rosin acids, eg, dehydro abietic acid, are similar to fatty acid ethoxylates in surfactant properties and manufacture, except for thek stabiHty to hydrolysis. No noticeable decomposition is observed when a rosin ester of this type is boiled for 15 min in 10% sulfuric acid or 25% sodium hydroxide (90). Steric hindrance of the carboxylate group associated with the aHcycHc moiety has been suggested as the cause of this unexpectedly great hydrolytic stabiHty. 

Maltol — see Pyran-4-one, 3-hydroxy-2-methyl-Maltol, ethyl — see Pyran-4-one, 3-ethoxy-2-methyl-Maltol, methyl — see Pyran-4-one, 3-methoxy-2-methyl-Mandelic acid ethyl ester, 1, 310-311 Manganaindene reactions, 1, 671 Mannich bases dehydro... 

The submitters have shown that these reactions proceed by dehydro-chlorination of the acid chloride to the ketene, which is then trapped by reaction with the phosphorane. The resulting betaine decomposes to the allenic ester via an oxaphosphetane. In contrast, the reaction of acid chlorides with 2 equivalents of phosphoranes involves initial acylation of the phosphorane followed by proton elimination from the phosphonium salt. ... 

Abietylamine, dehydro-, A tnfluoro- [Acetamide, 2,2,2-trifluoro-/V-[ [1,2,3,4,4a, 9,10,1 Oa-octahydro-l, 4a-dtmethyl-7-(l-methylethyl)-l -phenanthrenyl ] -methyl]-, [17 (la,4ad,10aa))-, 125 Acetamides, A-arylalkyl-, 7 Acetanilide, 2,2,2-tnfluoro- [Acetamide, 2,2,2-tnfluoroTV-phenyl-], 122 Acetic acid, cyano-, methyl ester, 63 Acetic acid, methoxy-, 70 Acetic acid, phenoxy-, 68 Acetic acid, phenyl- [Benzeneacetic acid],... 

The phosphonate (176) has been used for the addition to aldehydes of a masked jS-keto-ester function and applied in the synthesis of ( )-7(f),9(t)-trisporic acid B methyl ester. The isomerically pure phosphonate (177) has been used in a synthesis of dehydro-Cig juvenile hormone," the anion being generated by treatment with lithium di-isopro-pylamide in THF-HMPT at - 65 °C for 1 min. 

S1 C10H15NO2 94 2,3-Dehydro-2-methoxyca rbonyltropane (anhydroecgonine methyl ester) Er 1... 

Occurring Acetylene Compounds. VIII. The Synthesis of Methyl n-Dec-2-en-4 6 8-triynoate, an Isomer of the Naturally Occurring Dehydro-matricaria Ester. Acta Chem. Scand. 6, 602 (1952). 

Acetylene Compounds. V. Dehydro Matricaria Ester (Methyl n-decene-triynoate) from the Essential Oil of Artemisia vulgaris L. Acta Chem. Scand. 4, 1567 (1950). 

Treatment of A8(9)-dehydro-D-homoestradiol (39, R = H) (or its 3-methyl ether, R = Me) with Et3SiH/TFA followed by saponification of the trifluoroac-etate ester intermediate leads to D-homoestradiol (40) (or its 3-methyl ether) containing 2-15% D-homoequilenol (41) (or its 3-methyl ether).240 By contrast, reduction and saponification of 3,17-diacetyl-A8(9)-dehydro-D-homoestradiol (39, R = AcO) gives a 60% yield of D-homoestradiol without the presence of any D-homoequilenol (Eq. 87).240... 

Similarly, methyl methacrylate reacts with ketones and TMSH/RuCE-SlEO to give /l-trimethylsiloxy-2,2-dimethyl methyl esters in good yields. A lactone example is shown in Eq. 292.473 Methyl acrylate, trans methyl ( )-cinnamate, and 3,4-dehydro-S-lactone react in an analogous manner, albeit in lower yields.473... 

The bulk of the ester group has little effect on optical purity of N-acetylphenylalanine ester products formed from the dehydro substrates using the C-4 catalyst, and with this or the DIOP system, variation of the substituent in the phenyl ring of the N-acetylphenylalanine precursors also had little effect (242). 

L/Rh = 2 SCR=500 (aromatic enamides), 50 (/i-dehydro amino acid esters) and 1000 for the other substrates. 

On the other hand, esters of dehydro a-amino acids dimerize at 145°C in the absence of solvent to give 44 after a [4 + 2]-cycIodimerization and... 

Cannabidiolic acid pF nz Cannabidiolic acid-tetrahydro-cannabitriol ester Pl snz Cannabidiorcol Pl snz Cannabidivarin Pl snz Cannabidivarol picsi46,csi72 Cannabidivarolic acid pF us Cannabielsoic acid A Pl snz Resin ° Cannabielsoic acid B, C-3 Pl siyz Resin Cannabielsoic acid B Pl snz Resin ° Cannabielsoic acid, C-3 pF nz Cannabielsoin I, dehydro Resin ... 

Cyclization of a dipeptide having a hydroxylamine unit at the N-terminus is the second general method for the synthesis of 1-hydroxypiperazine-2,5-diones. Thus, Japanese workers have reported that the N-bromoacetyl derivatives (210) obtained from the corresponding dehydro amino acid esters, on treatment with hydroxylamine, give low yields of 1-hydroxy-3-alkylidenepiperazine-2,5-diones (211) (78BCJ550). The corresponding iodo compounds lead to better yields, whereas the chloroacetyl derivative does not cyclize under these conditions. 

More practical methods involve the dehydrohalogenation [100], dehydro-cyanation [101], or stereospecific bimolecular -elimination of mesitoate esters using potassium t-butoxide in dimethyl sulfoxide [102] as described in Eqs. (40H42). 

It was also reported that 7V-acyl-/V-hydroxyamino acids are readily synthesized from a-bromo esters 130 and dehydrated to form the dehydro compounds. A number of N-terminal Gly dipeptides having AAla, AAbu, ANva, and APhe at the C-terminus have been prepared in this manner. 131-133 ... 

H- 1,4-Thiazines and benzothiazines undergo oxidation to dehydro dimers (83) and (84) which are of considerable interest as they are the parent chromophores of the trichosiderin (trichochrome) pigments which occur in mammalian red hair and in the feathers of some birds (74T2781). In the case of monocyclic thiazines, reagents such as nitrobenzene or picric acid are required, but air oxidation is sufficient in the bicyclic series. It is curious that whereas aerial oxidation of the ester (85) gives both the dehydro dimers (86) and (87), ethyl azodicarboxylate only yields the tautomer (87) <70AC(R)35l). 

Hasegawa et al. (56) dj ected the enzymic conversion of 19-deoxylimonoic acid 3-methyl C ester to the 17-dehydro derivative by albedo tissue slices of Navel oranges. They isolated the product and identified it by TLC as the reaction product formed when the substrate was dehydrogenated by limonoate dehydrogenase (EC 1.1.1)... 

Ethers and esters derived from the alcohol also show activity in vivo. The ring structure of retinol ((i-ionone), or the more unsaturated ring in 3-dehydroretinol (dehydro-P-ionone), is essential for activity hydrogenation destroys biological activity. Of all known derivatives, all-/ran,v-retinol and its aldehyde, retinal, exhibit the greatest biological potency in vivo 3-dehydroretinol has about 40% of the potency of all-bms-retinol. 

Sparteine Group.—The new alkaloids calpurmenine (7) and its 2-pyrroloyl derivative (8) and the known compound 10,13-dihydroxylupanine were isolated from the South African plant Calpurnia aurea ssp. sylvatica but were absent from the Ethiopean C. aurea ssp. aurea.5 The structure of calpurmenine 12,13-dihydroxylupanine) was established by X-ray analysis of the ester (8).21 Another new alkaloid, 5,6-dehydro-a-isolupanine (9) was shown by g.l.c.-... 

Murofushi et al. (8) protected the 16,17 double bond of GA5 methyl ester by forming the epoxide with metachloroperben-zoic acid. After catalytic reduction of the 2,3 double bond they restored the exomethylene group by treatment with a mixture of sodium iodide, sodium acetate and zinc and hydrolyzed the methyl ester to obtain [2,3-3h2]GA2o Yakota et al. (81) prepared [2,3-3h2]GASelective catalytic reduction of the 3-methane-... 

Although it has been stated that only phenols are conjugated with sulfuric acid,1 three urinary steroid sulfate esters (androsterone sulfate, dehydro-epi-androsterone sulfate, and A 6-aZZo-pregnene-3(/3)-ol-20-one sulfate) have been isolated in which the sulfuric acid is esterified by an alcoholic hydroxyl group.111 It is true that no alcohol administered to... 

Ligand Variations in the Rh-Catalyzed Hydrogenation of Dehydro-Amino Acids and Esters... 

Obviously a substructure search within the >15000 alkaloids [23] known will uncover many compounds with a 1,4-relationship between a nitrogen atom and a carboxylic acid functionality, a carboxamide, or a carboxylic acid ester ( 1100 examples) [23]. Also anthranilic acid might be regarded as a 2,3-dehydro /1-amino-acid. However, these formal /1-amino acids [139] will not be discussed further, because we do not see a general biogenetic relationship with the real /1-amino acids (vide infra). 

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