Thioethers ethyl esters

Thio-l,7-naphthyridines appear to be represented by only two thioethers, 4-oxo-8-phenylthio-l,4-dihydro-l,7-naphthyridine-3-carboxylic acid (1, R = H) and its ethyl ester (1, R = Et) (see Section 15.3),157 and a few peripheral sulfur-containing 1,7-naphthyridines (see Section 18.2). 

Methyl thioethers Ethyl ketones Methyl esters Benzene... 

A soln. of Ag-nitrale and pyridine in ethanol added to a satd. hot ale. soln. of N-carbobenzoxy-L-phenylalanyl-S-trityl-L-cysteinylglycine ethyl ester, and the product isolated after 2 hrs. at room temp. N-carbobenzoxy-L-phenylalanyl-L-cysteinylglycine ethyl ester Ag-mercaptide (Y 90-98%) suspended in dimethyl-formamide, coned. HCl added, shaken 2 hrs. at room temp., then heated 1 min. on a water bath -> N-carbobenzoxy-L-phenylalanyl-L-cysteinylglycine ethyl ester (Y 80%). F. e., also protection as diphenylmethyl thioethers, s. L. Zervas and I. Photaki, Am. Soc. 54, 3887 (1962) f. S-protective groups s. Am. Soc. 55, 1337 (1963). 

In addition to 1,2-alkyl shifts, sulfonium ylides with P-hydrogen can also undergo fragmentation into an olefin and a thioether [1317,1318]. When allylic thioethers are treated with two equivalents of ethyl diazoacetate in the presence of a catalyst for diazodecomposition, S-alkylation and elimination of the thioalkyl group from the initially formed a-alkylthio-4-alkenoic esters occurs to yield 2,4-dienoic esters [1319]. 

The addition of a phenylsulfoxide moiety to the end of the side chain markedly changes the activity of this class of compounds. This product, sulfinpyrazone (97-11), stimulates uric acid excretion, making it a valuable dmg for dealing with the elevated serum uric acid levels associated with gout. The compound is stiU one of the more important uricosuric agents available today. The starting ester (96-9) is available by alkylation of the dianion from ethyl malonate with 2-chloroethylphenyl thioether. Condensation with diphenylhydrazine (97-3) in the presence of a base then affords the pyrrazolodione (97-10). Oxidation of sulfur with a controlled amount of hydrogen peroxide leads to the sulfoxide and thus sulfinpyrazone (97-11) [107]. 

The C-C bonding in R2 has been replaced by ether, thioether, amide or ester bond without losing sweetness. Rx is a small side chain such as a methyl, ethyl, isopropyl, or hydroxymethyl group, or an ester having a small substituent. The exact chemical nature of these groups is not crucial. 

From Table III it is apparent that a number of different donors could be used to obtain very attractive fractionation factors. Indeed, at 30°C., the isotopic equilibrium constant was 1.03, or more, for phenetole, anisole, diethyl ether, ethyl formate, dimethyl selenide, dimethyl sulfide, and diethyl sulfide. However, all of these donors were not equally satisfactory for our purpose. The boron trifluoride complexes of the thioethers, the selenide, and the ester had a pronounced tendency toward irreversible decomposition and were too unstable to be seriously considered for an... 

The types of compounds presently known to donate a hydrogen atom to photoexcited quinones include aldehydes, primary and secondary alcohols, esters and lactones, ethers and thioethers, olefins having allylic hydrogen atoms, alkylbenzenes, benzene, and saturated hydrocarbons. This list is undoubtedly incomplete. Acetone, methyl ethyl ketone, acetic acid, and -butyl alcohol react extremely slowly. 

The presence of sulfur volatiles has now been reported in a wide range of fruits and has been found to correlate well with quality in strawberries (9) and black currant buds (JO). Detailed studies of the volatiles in pineapple (11,12,13) also reported the presence of several thioether esters including methyl (methylthio)acetate, ethyl (mediylthio)acetate, 3-(methylthio)propyl acetate, methyl 3-(methylthio)propanoate, ethyl 3-(methylthio)propanoate and the alcohol, 3-(methylthio)propan-l-ol. The sulfur esters 3-(meAylthio)propyl acetate and ethyl 3-(methylthio)propanoate were also detected in Asian pears (14), and fifteen sulfur volatiles, including 3-(methylthio)hexyl acetate, have recently been reported in yellow passionfruit (15). 

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