Isopropyl 3- propionate from

The reaction of 1-isopropoxy-l-trimethylsiloxycyclopropane (1, R = i-Pr) with TiCl yields the titanium homoenolate of isopropyl propionate 2 (R = i-Pr) and Me3SiCl (Eq. see 9). That of 23, in contrast, yields a considerable fraction of the homoenolate of silyl propionate as well, Eq. (66) [19]. Apparently, the loss of an isopropyl group from an oxygen-stabilized cationic intermediate competes with that of the silyl group with bulky substituents. 

The C-12 to C-17 segment (645) of ( + )-aplasmomycin has been synthesized from 590 as shown in Scheme 94 [148]. In the first step, an aldol condensation of isopropyl propionate enolate with 590 produces 638 as a mixture of isomers. After conversion to enone 640, reduction of the carbonyl with NaBH4-CeCl3 gives alcohol 641 as a single isomer. A second reduction of642 with zinc borohydride gives a separable mixture of isomers, the major isomer... 

Stull Mimmun/cs the data available on the vapor pressures of acetic anhydride and ethyl formate from the melting point to tile critical point, and for propionic anhydride and isopropyl acetate up to the boiling point 1 The vapor pressures ubove the boiling point were estnriuccd by a previously described method ... 

The liquid viscosities ol acetic anhydride and propionic anhydride have been reported in the literature from 0 C to IWPC A limited amount of data are available on ethyl tor mate and isopropyl acetate.,r Constants for the equation of Van Wizen. Cardo/o. and Lnngcnkump were calculated for isopropyl acetate.3 Constants for the other three compounds are available 1... 

The Influence of Substituents. The substituents at the groups indicated have a markedly smaller effect on z and t. This is evidence for the orientation of the molecules with their reacting atoms toward the catalyst (Fig. 13), as is required by the theory. The influence is particularly slight in the case of metals. For hydrocarbons (Nos. 1-3), amines (23-29), and alcohols Z — 1 and z3 = 0. From a crisscross examination of the data of Nos. 40-47, it can be seen that in the case of copper not only the values of z2 but also those of a2 are practically the same for ethyl, n-propyl, isopropyl alcohols, acet- and propionic aldehydes, and also acetone. This was explained by the author (66) in a treatment of the above-mentioned model from the standpoint of statistical mechanics. It was found that... 

Eight naturally occurring, structurally related avermectins are produced by Streptomyces avermitilis [7], The avermectin polyketide structure is derived from seven acetate and five propionate residues, together with a single 2-methylbutyric acid or isobutyric acid residue which forms the sec-butyl or isopropyl group attached to the C25 of the spiroketal moiety [8,9] (Fig. 1). The avermectin agly-cone is further modified by glycosylation at C13, with the attachment of two O-methylated oleandrose residues and O-methylation at C5. Thus, S. avermitilis... 

As discussed earlier, the avermectin polyketide backbone is derived from seven acetate and five propionate extender units added to an a branched-chain fatty acid starter, which is either (S( I )-a-mcthylbutyric acid or isobutyric acid. The C25 position of naturally occurring avermectins has two possible substituents a. sec-butyl residue derived from the incorporation of S(+)-a-methy lbutyry 1-CoA ( a avermectins), or an isopropyl residue derived from the incorporation of isobutyiyl-CoA ( b avermectins). These a branched-chain fatty acids, which act as starter units in the biosynthesis of the polyketide ring, are derived from the a branched-chain amino acids isoleucine and valine through a branched-chain amino acid transaminase reaction followed by a branched-chain a-keto acid dehydrogenase (BCDH) reaction (Fig. 5) [23]. 

Rhone-Poulenc developed ketoprofen [66]. A few synthetic routes have been reported that involving multi-step syntheses [67, 68]. Ketoprofen is produced by similar reaction sequences that were described for naproxen [69]. Transition metal-catalyzed reactions including carbonylations, hydroformylations, and hydrogenations have been applied to the synthesis of ketoprofen. 3-Vinylbenzophenone (4) was obtained from 3-bromo-benzophenone (3) by a Heck reaction. Palladium-catalyzed carbonylation of 4 provided the isopropyl-a-(3-benzoylphenyl)propionate in 95% yield. Ketoprofen was then obtained in 90% yield by hydrolysis of the isopropyl ester [69]. 

The effect of detoxification of the medium by removal of toxic compounds with UF membranes was demonstrated by Boyaval et al. [36] in the fermentation of propionic acid. UF runs led to an eightfold increase in volumetric productivity relative to fed batch experiments. The effectiveness of membrane bioreactors in the lowering of toxicity of the compounds involved in the bioconversion system was demonstrated by Edwards and co-workers [159]. An eightfold increase in the removal of phenoHc compounds from effluents was observed when polyphenoloxidase was immobilized in a capillary poly(ether)sulfone membrane as compared to the use of the free enzyme. Butanol recovery from the fermentation medium with organic solvent extraction or membrane solvent extraction led to similar results, both processes leading to decreased product inhibition. Due to the low toxicity of the extractive solvent used (isopropyl myristate) on Clostridium beyerinckii cells, no protective effect of the membrane was observed. However, precipitates observed in two-Hquid phase extraction were not observed... 

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