Ether Derivatives External

The application of the usual alkylating procedures of organic chemistry to the sugars and derivatives gives sugar ethers. Except for the glycosidic 

Many fully and partially methylated sugars have been characterized to serve as reference compounds for structural determinations (5). 

Numerous ethers of cellulose, starch, and bacterial dextran are of established or potential industrial importance. (See also Chapter XII.) Treatment of the polysaccharides with alkali and methyl chloride, ethyl chloride, benzyl chloride, ethylene oxide (or ethylene chlorohydrin), sodium chloro-acetate, and allyl bromide gives, respectively, the methyl, ethyl, benzyl, hydroxy ethyl, carboxy methyl, and allyl ethers. The cellulose derivatives 

Of considerable interest are the co-(p-aminoacetophenone) ethers of cellulose containing about one ether group for each three glucose units 10a). These may be diazotized and coupled to provide cellulose-azo dyes, and the latter may be rendered water-soluble by carboxymethylation. 

The allyl ethers of sugars and glycosides polymerize in the presence of oxygen. They are prepared best by treatment of glycosides with allyl bromide and alkali 11). 

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Tomioka and coworkers first reported the stoichiometric and catalytic asymmetric 1,2-addition of organoUthium reagents to N-arylimines mediated by an external chiral ligand [66-69]. The chiral p-amino ether derivative 15 is an excellent asymmetric controller [70] which works as a catalyst even in substoichi-ometric amounts. Using organoUthium reagents (R=Me, Bu, Ph, vinyl), aryl- or... 

Species of the genus Vellozia have been extensively studied for their flavonoid complement in relation to chemosystematics. In addition to a series of C-methylflavonols and two C-prenylated flavonols, derivatives of vellokaempferol and velloquercetin are accumulated in whole plants, leaves, and leaf exudates. The basic structure of these compounds is characterized by 7,6-isopropenylfurano substitution, based upon kaempferol, quercetin, and their 0-methyl ethers. In addition, 8-C-methyl derivatives of these compounds were also identified from leaves of V. stipitata " So far, species of this genus are the only reported sources of these compounds, which in parts have been proved to be accumulated externally. ° Structures are exemplified by Figure 12.10. 

Many patents have been issued on the use of pyrogallol derivatives as pharmaceuticals. Pyrogallol has been used externally in the form of an ointment or a solution in the treatment of skin diseases, eg, psoriasis, ringworm, and lupus erythematosus. Gallamine triethiodide (16) is an important muscle relaxant in surgery it also is used in convulsive-shock therapy. Trimethoprim (2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine) is an antimicrobial and is a component of Bactrin and Septra. Trimetazidine (l(2,3,4-trimethoxybenzyl)piperazine (Vastarel, Yosimilon) is used as a coronary vasodilator. l,2,3,4-Tetrahydro-6-methoxy-l-(3,4,5-trimethoxyphenyl)-9.H-pyrido[3,4- ]indole hydrochloride is useful as a tranquilizer (52) (see HYPNOTICS, SEDATIVES, anticonvulsants, and anxiolytics). Substituted indanones made from pyrogallol trimethyl ether depress the central nervous system (CNS) (53). Tyrosine-and glycine(2,3,4-trihydroxybenzyl)hydrazides are characterized by antidepressant and anti-Parkinson activity (54). 

Intramolecular oxidative cyclizations in the appropriately substituted phenols and phenol ethers provide a powerful tool for the construction of various practically important polycyclic systems. Especially interesting and synthetically useful is the oxidation of the p-substituted phenols 12 with [bis(acyloxy)iodo]-arenes in the presence of an appropriate external or internal nucleophile (Nu) leading to the respective spiro dienones 15 according to Scheme 6. It is assumed that this reaction proceeds via concerted addition-elimination in the intermediate product 13, or via phenoxenium ions 14 [18 - 21]. The recently reported lack of chirality induction in the phenolic oxidation in the presence of dibenzoyltar-taric acid supports the hypothesis that of mechanism proceeding via phenoxenium ions 14 [18]. The o-substituted phenols can be oxidized similarly with the formation of the respective 2,4-cyclohexadienone derivatives. 

In suitable vinylic halides, nucleophilic photosubstitution occurs intramolecular- 295-297,324,330-332 por jnstance irradiation of 113 in methanol only yields benzofuran 114, and no vinyl ether product or 1,2-aryl rearrangement products are formed (equation 84a)296. Apparently, the reaction with an internal nucleophile is faster than the 1,2-aryl shift and also faster than the reaction with an external nucleophile. With the less stabilized vinyl cations derived from the a-methyl- and a-H-analogues of 113-OMe, 1,2-aryl shifts do... 

Enamines may be reduced by sodium borohydride to give saturated amines, but only if a protonating species is available to convert the enamine initially into the iminium cation (lo). Steroidal g-amino-g,5-dienes are unreactive to sodium boro-hydride alone, but addition of acetic acid leads to rapid reduction via the iminium ion (10) to give gj -amino-A -steroids [224], The possibility that diborane was the reactive species in the NaBHd/HOAc system was excluded by the virtual non-reactivity of the enamine to externally generated diborane. Reduction of the iminium ion derivative (3) of a 6-formyl enol ether has been exploited in a variant of the Vilsmeier synthesis of 6-methyl steroids [22 ], the reduction product was the 6-aminomethyl enol ether (ii) which suffered hydrogenolysis with Raney nickel to give the 6-methylated enol ether (12). 

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