Propionate esters

Liquid crystal polyesters are made by a different route. Because they are phenoHc esters, they cannot be made by direct ester exchange between a diphenol and a lower dialkyl ester due to unfavorable reactivities. The usual method is the so-called reverse ester exchange or acidolysis reaction (96) where the phenoHc hydroxyl groups are acylated with a lower aHphatic acid anhydride, eg, acetic or propionic anhydride, and the acetate or propionate ester is heated with an aromatic dicarboxyHc acid, sometimes in the presence of a catalyst. The phenoHc polyester forms readily as the volatile lower acid distills from the reaction mixture. Many Hquid crystal polymers are derived formally from hydroxyacids (97,98) and thein acetates readily undergo self-condensation in the melt, stoichiometric balance being automatically obtained. 

Acetate propionate esters are nontoxic, exhibit excellent clarity and high tensile strength, and can be formulated into hot-melt dip coatings for food (168). Alternatively, they may be dissolved in volatile solvents and appHed to foods in the form of a lacquer coating (169). 

Propionate Esters Methyl propionate Ethyl propionate Butyl propionate Amyl propionate... 

Benzyl Acetate.—This ester is a constituent of the oils of jasmin, ylang-ylang, and similar flower oils. It has not a very intense odour, but is essential to the successful production of such perfumes as artificial jasmin. It has the formula CgHg, CH2. O. OCCH3. It is a colourless oU, boiling at 206° at ordinary pressure, and has a specific gravity 1-0570 at 16° and a refractive index 1-5034 . The propionic ester has the formula C0H5CH2OOCCH2CH3, and closely resembles the acetate in odour. 

Phenyl-ethyl Propionate.—The propionic ester of phenyl-ethyl alcohol has the formula CgHj. . OOC. CH CHg. It has a pronounced... 

Dialkyl phosphites are added to unsaturated compounds in the presence of sodium ethylate or triethylamine forming, for instance, 2-(dialkylphosphono) propionic ester [152]. The same compounds are obtained by catalytic conversion of phosphites with propiolactones [153,154] see Eq. (85) ... 

E. J. Corey, Y. Bo, J. Busch-Peterson, Highly Enantioselective Phase Transfer Catalyzed Alkylation of a 3-Oxygenated Propionic Ester Equivalent Application and Mechanism , J. Am Chem Soc 1998, 120, 13000-13001. 

The glycosidic conjugates 88 were prepared by reaction of 3-hydroxymethylpurpurin-l 8-iV-hcxylimidc-l 7-propionic ester 87 with the... 

The derivative 90 was obtained by condensation of the purpurin-18-A-hexylimide-17-propionic acid with aminolactose heptaacetate in the presence of benzotriazol-l-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP) followed by the deacetylation procedure. The lactose-photosensitiser conjugate linked by an ethylene moiety was also prepared by following a similar approach. The purpurin-18-methyl ester 81 was converted into /V-(3-iodobenzyl)/ /evo-purpurin-18-7V-hexylimide-17-propionic ester by hydrogenation over Pd/C followed by reaction with 3-iodo-benzylamine. Afterwards, the propargyllactose heptaacetate reacted with A-(3-iodobenzyl)rMeio-purpurin-18-A-hexylimide-l 7-propionic ester in the presence of tris(dibenzylidieneacetone)dipalladium(0) (Pd2-dba3) which, after deacetylation conditions, afforded the derivative 89 (Fig. 9).68... 

Extensive investigations have been directed toward the development of chiral ester enolates that might exhibit practical levels of aldol asymmetric induction. Much of the early work in this area has been reviewed (111). In general, metal enolates derived from chiral acetate and propionate esters exhibit low levels of aldol asymmetric induction that rarely exceed 50% enantiomeric excess. The added problems associated with the low levels of aldol diastereoselection found with most substituted ester enolates (cf. Table 11) further detract from their utility as effective chiral enolates for the aldol process. Recent studies have examined the potential applications of the chiral propionates 121 to 125 in the aldol condensation (eq. [94]), and the observed erythro-threo diastereoselection and diastere-oface selection for these enolates are summarized in Table 31. For the six lithium enolates the threo diastereoselection was found to be... 

The sulfones 367 (R = H and Me) obtained from 3-(indol-3-yl)propionate esters with the anion of dimethyl sulfoxide were cyclized, losing methylthiol, via 368 in the presence of p-toluenesulfonic acid in hot acetonitrile, ... 

Catalytic hydrogenation of the formyl derivative (36-4) proceeds as usual from the more open a face of the molecule to afford the axial 2 3 methyl derivative (37-1). Treatment with a strong base leads to epimerization to the more stable equatorial 2a methyl isomer. There is thus obtained the androgen, dromostanolone (37-2) [35]. The compound is used clinically as its 17-propionate ester. Direct reaction of the formyl ketone (36-4) with hydrazine leads to the formation of a fused pyrrazole ring [36] this product is the widely used androgenic and anabohc drug, stanazole (37-3). 

Methanol and ethylene glycol detected as propionate esters (166). 

Two groups independently reported the formation of titanium homoenolates by the transmetalation reaction of 3-stannyl-propionate esters with TiCl, Eq. (48) [45, 46]. Amide homoenolates become available along this route [47], The trichlorotitanium species thus obtained have been shown ( H NMR) to be similar to that generated along the siloxycyclopropane route and indeed exhibit very similar reactivities. This method does provide a conventient alternative to the siloxycyclopropane route. 

Figure 5 Typical mass spectrum (A.H.I. MS12) of mesoporphyrin-IX dimethyl ester (46). Note the typical fragmentation pattern of the propionic ester side chain at m/e 579 (-Me), 563 (-OMe), 535 (-C02Me) and 521 (-CH2C02Me)...

Cellulose esters of the 2-.. 3-. and 4-carbon acids are readily prepared by the cellulose-anhydride reaction the acetate ester and the mixed acetate butyrate and acetate propionate esters arc manufactured and used in large amounts. Esters of higher acids require different synthesis techniques and tend to be prohibitively expensive except as specialty products. Some arc in commercial production, however. Cellulose acclalc phlhalatc, for example, is manufactured for use as an enteric coating on pills. 

When, sodium ethoxide or sodamide acts on acetic or propionic ester, 2 mols. of the ester condense to yield acetoacetic or propiopropionic ester respectively. In the reaction 1 mol. of alcohol is split off from 2 mols. of ester, the ethoxyl group coming from one molecule, and the hydrogen atom from the a-carbon of a second. 

Replacement of the acetyl group in Aceklidine by homologous acyl groups leads at first (propionic ester) to a decrease in cholinomimetic activity and then (butyric and isovaleric esters) to the appearance of cholinolytic properties. 

Whereas the lithium enolates of acetate and propionate esters of difluoroallylic alcohols are known to fragment rapidly, methoxy- and benzyloxy-acetates have been found151 to form chelated enolates which undergo a smooth [3,3]-sigmatropic rearrangement as their silyl ketene acetals to afford highly functionalized difluoro compounds (see Scheme 33). Allenic silyl ketene acetals (117) have been used152 to prepare 2-substituted methyl 3,4-dienoates (118). 

In the total synthesis of optically active erythromycin A reported by Woodward and collaborators (87), the bicyclic compound 142 (Fig. 1) was used to produce the two segments Cg-C)5 (143) and Cg-Cg (144) of erythronolide A. These two segments were then combined (-145) and converted into 146). Aldol condensation of a propionate ester derivative with 146 gave the erythronolide A secoacid derivative J 47 (Fig. 2) which was successfully transformed into erythromycin A (149) through a series of chemical transformations where compound 148 was one of the key intermediates. 

Access to analogues with higher substitution was easily achieved. From either the propionate ester 193 or acetic acid 188, we previously made the propionic acid appendaged 189, which was in turn alkylated to the gem-dimethyl acid 194 in 76% yield (93% based on recycled starting material). The vinylsilane of 194 underwent addition of ozone to eventually afford hydroperoxide 195, and final ring closure was accomplished with trifluoroacetic acid and acetone to afford gem-dimethyl analogue 169 in 19% overall yield from 194 (Eq. 20). 

Vitamin A (IFN 7-05-142), as the acetate ester, palmitate ester, propionate ester or a mixture of these esters. 

Ml - ANDR0ST-5-ENE-3-beta.17-beta-DIOL, 17-PROPIONATE (ester)... 

HI - 2-BUTANOL, 9-CD1HETHYLAMINO )-3-METHYL-l 2-01PHENYL- PROPIONATE (ester), HYDROCHLORIDE, ( )-... 

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