Methyl ethers optical rotation

It is well known that spontaneous resolution of a racemate may occur upon crystallization if a chiral molecule crystallizes as a conglomerate. With regard to sulphoxides, this phenomenon was observed for the first time in the case of methyl p-tolyl sulphoxide269. The optical rotation of a partially resolved sulphoxide (via /J-cyclodextrin inclusion complexes) was found to increase from [a]589 = + 11.5° (e.e. 8.1%) to [a]589 = +100.8 (e.e. 71.5%) after four fractional crystallizations from light petroleum ether. Later on, few optically active ketosulphoxides of low optical purity were converted into the pure enantiomers by fractional crystallization from ethyl ether-hexane270. This resolution by crystallization was also successful for racemic benzyl p-tolyl sulphoxide and t-butyl phenyl sulphoxide271. 

A large number of polyfructosans that have been reported from time to time by different authors have been investigated by Schlubach and his associates. In order to obtain polysaccharides of constant optical rotation, 100 to 300 precipitations from aqueous solution by the addition of alcohol were necessary. Fifty to 150 precipitations from chloroform solution with petroleum ether were required for purification of the acetate derivatives. These were methylated according to the procedure of Haworth and Straight,24 and upon hydrolysis partially methylated fructoses were obtained. 

Section II, 1. Theoretical aspects of asymmetric polymerization have been discussed by Fueno and Furdkawa [T. Fueno, J. Furukawa J. Polymer Sci., Part A, 2, 3681 (1964)]. 1-phenyl-l,3-butadiene has been polymerized using (R)-2-methyl-butyl-lithium or butyl-lithium complexed with menthyl-ethyl-ether, yielding optically active polymers with [a] f, referred to one monomeric unit, between +0.71 and —1.79. Optical rotation dispersion between 589 m u and 365 mft is normal and the Drude equation constant is comprised between 255 raft and 280 raft [A. D. Aliev, B. A. Krenisel, T. N. Fedoiova Vysokomol. Soed. 7, 1442 (1965)]. 

Tables II to X give the melting points and, where applicable, the optical rotations of the inositols, inososes, inosamines, and quercitols, and of all of their known O-substituted derivatives. Anhydroinositols, although not substitution products in the strict sense, are included, as are the carbonyl-functional derivatives of the inososes. Halogen- and nitro-substituted cyclitols, and the C-methyl-inositols and their derivatives, are not included most of these compounds are referred to in the text. The derivatives are arranged in the following order salts (inosamines) or functional derivatives (inososes), carboxylic esters, borates, nitrates, sulfonic esters, phosphates, glycosides, acetals (and Schiff bases), ethers (and IV-alkyl derivatives), and anhydrides.

The acetates, nitrates, and methyl ethers of the Schardinger dextrins have been reported in crystalline form. There are over 20 reports on the preparation and properties (for example, the optical rotation) of -dextrin acetate from the work of Pringsheim alone. No attempt can be made to review the entire literature in this field, since most of it is only of historical interest. Rather the most recent or most reliable results will be summarized. 

Synthesis of the 3,4,6-trimethyl ether of 2-deoxy-2-methylamino-n-gluconic acid was carried out along lines similar to those of the synthesis of the 3,6-dimethyl ether. By the addition of methylamine and hydrogen cyanide to 2,3,5-tri-O-methyl-n-arabinose, followed by hydrolysis, only one compound was formed, and this was related to n-glucosamine on the basis of its optical rotation. An attempt to obtain the aldose derivative by reduction with sodium amalgam was not successful, probably because of the impossibility of 5-lactone formation. 

Finally, an attempt was made by using Buck and Kobrich s method (ref. 77), which yields phenols by the reaction of lithiated aryl compounds with nitrobenzene. Compound (81) was treated with n-butyllithium at -10010 in THF in the presence of tetramethylethylenediamine followed by the addition of nitrobenzene. The crude products, which were difficult to isolate as phenolic compounds, were immediately methylated with diazomethane in ether solution. The products were subjected to preparative thin layer chromatography, affording two substances. One, obtained from the upper layer, was recrystallized from ethanol as colorless needles. It showed mp 162.5 163.5lC and an optical rotation of [ o ]D -110° (c= 0.14 in CHClj). The other one, isolated from the lower layer, was recrystallized from ethanol as colorless needles. It showed mp 185 — 187"C and an optical rotation of... 

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