Methyl ethers degradation, oxidative

The trimethoxyphenanthrene obtained by the degradation of isothebaine methyl ether is oxidized by nitric acid to benzene-1 2 3 4-tetracarboxylic acid [5]. (Compare the production of the same acid as final product of oxidation of 3 4 6-trimethoxyphenanthrene [9-10].)... 

One of the first syntheses of enantiomerically pure brevicomin is likewise due to Mori. [203] The starting material is (D)-(-)-tartaric acid. After elongation of the carbon chain, one ester is selectively hydrolysed, and in three steps reduced to an ethyl group. The keto-fimction is introduced with ethyl acetoacetate. The methyl ethers are oxidatively degraded and the rings closed with acid catalysis to yield hrevicomin. 

Most structural work on xylan has been done on that from esparto grass and the principal attack made by way of the methyl ether. Xylan can be methylated by heating with methyl iodide and silver oxide,92-93 but complete etherification is difficult and considerable degradation probably occurs. On the other hand, complete etherification is attained by methylation in two operations with potassium hydroxide and dimethyl sulfate to give a dimethylxylan in almost quantitative yield70 showing [< ]22d — 92° in chloroform. Methylation with potassium hydroxide appears to proceed more readily than with sodium hydroxide.70-92... 

Diazomethane furnishes the methyl ether which has been degraded to 3-methoxyfuran which, however, is more easily available from 3-iodofuran. 3-Methoxyfuran is cleaved by acid to furan-3(2H)-one. Other 3-furanols with ester, acetyl or benzoyl substituents at the 2-position are also available. They exist in the enolic form but their chemistry has not been investigated (76JCS(P1)1688>. Furan-3(2H)-ones with acetyl or ester substituents at the 4-position are readily available. They exist in the keto form but show some evidence for enolic behaviour and their chemistry is similar to that of enolizable ketones. They enter into cycloaddition with maleic anhydride, are alkylated at the 2-position, condense with aldehydes and ketones and are oxidized by LTA to the 2-acetoxy compounds (74BSF2061). 

Following previous studies on lauryl sulfate and AES, Cuzzola et al. [44] also studied the Fenton oxidation products of AEO and NPEO. The aerobic biodegradation of AEO and NPEO and anaerobic biodegradation of NPEO were studied by Schroder [27] by means of FIA-MS and LC-MS and MS-MS in positive-ion and/or negative-ion APCI. Methyl ethers of AEO ate persistent in aerobic conditions. NPEO degradation results in NPEC. Anaerobic biodegradation of NPEO results in nonylphenols. 

Isocodeine methyl ether, prepared from the methyl ether methiodide [411] or by methylating isocodeine-N-oxide and reducing the product [265], cannot be isomerized to thebainone methyl enolate by heating with sodium ethoxide [265]. On degradation it yields y-codeimethine methyl ether [411]. 

Desoxycodeine-A is phenolic, being soluble in alkali, giving a colour with ferric chloride and forming a methyl ether [1]. The phenol may be degraded to a methine base [vi, R = H], which oxidizes rapidly in air, and the methyl ether to [vi, R = Me], which decomposes spontaneously to an amine and dimethylmorphol [vn] [1],... 

Tetrahydrothebaine [m] was first prepared by Schopf and Winter-halder [5] and shown to be identical with dihydromorphine dimethyl ether. It is best prepared from thebaine by hydrogenation of the hydrochloride in glacial acetic acid over platinum oxide [22-23], or of the base in ethanol over W. 6 Raney nickel [24]. It can be demethylated to dihydromorphine by hydriodic acid or aluminium chloride [22-23]. The Hofmann degradation has not been studied, but hydrogenation of a-oodeimothine methyl ether [xxxix] affords a-tetrahydrocodeimethine methyl other [xl], which is tetrahydrothebaine dihydromethino [25],... 

Hofmann degradation of isothebaine methiodide gives a resinous methine base degradation of which involves loss of trimethylamine and production tars [6], The oxidation of isothebaine and its methyl ether with iodine gives only green, amorphous substances [3]. 

While ethers react only slowly with dimethyldioxirane, they are efficiently hydroxylated by methyl(trifluoromethyl)dioxirane even at low temperatures. Thus r-butyl methyl ether [32] was converted to f-butyl alcohol through its hemiacetal. On the other hand, tetrahydrofuran gave butyrolactone [32] in which presumably the intermediary cyclic hemiacetal was oxidized to the lactone by an additional C —H insertion. The ketal was degraded into 2-butanone and the orthoformate into diethyl carbonate [32]. The latter transformation may serve useful for deketalation under neutral conditions. 

The fourteen alkaloids discussed in this section constitute a remarkable series of structurally and stereochemically interrelated substances. Superficially, all the alkaloids contain the same basic ring system, 5,10b-ethanophenanthridine (145), but alkaloids are elaborated from both enantiomorphs of this basic nucleus. Further variations are produced by differences in aromatic substitution and the functional groups attached to rings C.and D. It has been possible to interrelate all the alkaloids of this section through a combination of simple oxidation, reduction, and dehydration reactions coupled with four rather specific degradative techniques. These reactions are (1) aromatic demethoxylation by sodium and amyl alcohol (82), (2) replacement of OH by H via the action of lithium aluminum hydride on an intermediate chloro compound (146), (3) acid hydrolysis of ally lie methyl ethers to alcohols (147, 148), and (4) 0-methylation of hydroxylic alkaloids with... 

Reduction of an aldose forms one alditol reduction of a ketose forms two alditols. Br2 oxidizes aldoses, but not ketoses ToUens reagent oxidizes both. Aldoses are oxidized to aldonic acids or aldaric acids. Aldoses and ketoses react with three equivalents of phenyUiydrazine, forming osazones. C-2 epimers form identical osazones. The Kiliani-Fischer synthesis increases the carbon chain of an aldose by one carbon— it forms C-2 epimers. The Ruff degradation decreases the carbon chain by one carbon. The OH groups of monosaccharides react with acetyl chloride to form esters and with methyl iodide/silver oxide to form ethers. 

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