Pendent ethyl groups

Because of the pendent methyl groups on the propylene oxide side chains, hydroxypropylcellulose is much more lipophilic than HEC. This allows HPC to dissolve in and thicken many organic systems such as ethyl alcohol, aqueous ethyl alcohol, and propylene glycol. Hydroxypropylcellulose is also thermoplastic it can be melt-processed as films, fibers, and structural components. The methyl groups on HPC can create hydrophobic domains, which help explain why highly concentrated solutions of HPC exhibit liquid crystalline morphology (151). 

The first total synthesis of racemic histrionicotoxin (58), the parent structure in a family of related spirocyclic alkaloids isolated from the skins of Dendrobates histrionicus, utilized the Eschenmoser reaction to generate the anchor of what would become the enyne group extending from the a-position of the piperidine nucleus. The spirothiolactam intemiediate (77) was condensed with ethyl 2-bromoace-toacetate in the presence of sodium bicarbonate to produce (78) in good yield (Scheme 18). Prior to further reaction on the vinylogous carbamate, the pendent allylic acetate was elalx>rated to the enyne (79). Subsequent deacylation and enyne protection yielded spirobicycle (80), which gave a 1 1 mixture of isomers upon reduction. The desired diastereomer (81) was isolated and subsequently converted to racemic histrionicotoxin (58). 

A pendent mercury drop electrode has been used to reduce the 4,5-azomethine group in 1,4-benzodiazepines There were additional contributions from partial reduction of nitro moieties, as in nitrazepam, and A -oxides, as in chlordiazepoxide. The 5-lipoxygenase inhibitor methyl 2-[(3,4-dihydro-3,4-dioxo-l-naphthalenyl) aminojbenzoate (CGS 8515) has been measured in ethyl acetate extracts of plasma from animals treated with the drug using an ODS-modified silica column with methanol-aq. acetate buffer (0.15 mol L, pH 4.5) (60 -f 40) as eluent and EC... 

Figure 4 Reaction scheme for ihe preparation of tyrosine-derived polyarylates. This reaction scheme is a copolymerization of a diphenol component and a diacid component. The diphenol components are the same desaminotyrosyl-tyrosine alkyl esters used in the synthesis of polycarbonates (Fiipire 3). The pendent chain Y is ethyl, butyl, hexyl, or octyl. The diatid components are succinic acid, adipic acid, suberic acid, and sebacic acid providing a flexible backbone spacer (R) having 2, 4, 6, and 8 methylene groups respectively. DIPC = diisopropylcarbodiimide.

Introduction of acidic and hydrophobic functions in the galleries of mixed phos-phonates yields attractive catalysts for the hydrolysis of ethyl acetate with improved efficiency (225). In another study, a-ZrRP containing sulfophenyl phos-phonic acid pendent groups, described earlier, was used to hydrolyze 1,3-ditholanes and 1,3-dithianes to the corresponding carbonyl compounds (226). Catalytic hydrolysis studies often use ethyl acetate as the substrate and monitor the production of acetic acid to evaluate the corresponding catalytic parameters. 

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