2-5-ethyl-2-thio preparation

Isomeric 6- and 8-chloro-7-fluorothiazolo[3,2-a]quinolines (768 and 769) were prepared in 29-66% yields by the thermal cyclization of [(2-sub-stituted ethyl)thio][(3-chloro-4-fluorophenyl)amino]methylenemalonates (767) in diphenyl ether at 250°C for 5 min (82EUP58392). 

Olah et al.457 have developed a mild method for the preparation of methyl and ethyl thio(dithio)benzoates. They prepared 5-methyl (5-ethyl) thiocarboxonium and dithio-carboxonium fluoroantimonates 121a and 121b by methylating (ethylating) carbonyl... 

Benzyl 1-thio-lactoside and ethyl lactoside, prepared from lactose dibenzyl dithioacetal116 by the preceding methods, are necessarily pyranosides (owing to the substitution on 0-4). Stevens and coworkers310 prepared ethyl 2,3 4,5-di-0-isopropylidene-l-thio-/3-D-glucoseptanoside by partial demercaptalation of 2,3 4,5-di-O-isopropylidene-D-glucose diethyl dithioacetal. 

Zervas48 through the catalytic reduction of 2,3,4,6-tetraacetyl-2-hydroxy-D-glucal, has recently been prepared by the reductive desulfurization of ethyl tetraacetyl-l-thio-/ -D-mannopyranoside (XL),47 a substance which has been obtained through the mercaptolysis of mannosidostreptomycin48 and may be prepared through the prolonged action of ethyl mercaptan and hydrochloric acid on D-mannose. 

Using the ethyl 1 -thio derivative (97) of 2,3,4-tri-O-benzoyl-D-xylose, the fully protected and free O-glycopeptides 99 and 100, having the TV-terminal amino acid sequence 3 to 6 (98) of the protein core of a proteodermatan sulfate have been prepared (69). 

In 1916, Schneider and Sepp 1 prepared ethyl 1-thio-a-glucofuranoside by treating an aqueous solution of one mole of the diethyl dithioacetal with one mole of mercuric chloride, and maintaining neutrality by neutralizing the hydrochloric acid formed with aqueous sodium hydroxide. The product was regarded by them os a normal (i.e., pyranoid) 1-thiogly-... 

The methyl, propyl, and benzyl 1-thio-a-D-glucofuranosides were prepared" by the original method (with neutralization by sodium hydroxide). Use of the method of Pacsu and Wilson" gave the methyl, ethyl, propyl, and isopropyl 1-thio-a-D-ribofuranosides in yields ranging from 65 to 80%. Sodium (methyl l-thio-a-D-glucofuranosid)uronate and the ethyl and propyl analogs were obtained 7 similarly from the sodium salt of the... 

Wolfrom and coworkers88-71 were able to prepare various 1-thio-a-D-galactofuranosides, generally isolated as the acetates, after purification by column chromatography. Thus, the Pacsu and Wilson method gave sirupy ethyl 1-thio-a-D-galactofuranoside, and a crystalline acetate. This product was also obtained by treatment of the dithioacetal with dilute hydrochloric acid and then mercuric oxide. Ethyl 2-acetamido-2-deoxy-l-thio-a-D-galactofuranoside was prepared in 32% yield, and the /3-d anomer in 3% yield. 

Whereas ethyl l-thio-d-D-arabinofuranoside cannot be prepared directly, the 5-O-benzoyl diethyl dithioacetal gave 38% of ethyl 5-O-benzoyl-l-thio-0-D-arabinofuranoside, which was debenzoylated to the desired product. The 5-benzoate of ethyl 1-thio-a-D-ribofuranoside was similarly prepared.88 Two other compounds, ethyl 2-acetamido-2-deoxy-l-thio-/3-L-arabino-furanoside72 and ethyl 2-acetamido-2-deoxy-l-thio-a-D-xylofuranoside,73 were prepared from the corresponding d-galacto and d-gluco analogs by periodate oxidation, and subsequent borohydride reduction of the product. 

A new route, from 1-thio-D-aldohexofuranosides, was developed by Wolfrom and coworkers ethyl 1-thio-a-D-glucofuranoside was converted by chlorine into the chloride,101 arid this was condensed with the chloro-mercuri derivative of a 2,6-diacetamidopurine to give, on partial deacetylation, a 2-acetamido-9- f-D-glucofuranosyladenine.70 D-Galactofuranosyl analogs were also prepared. 

On heating a solution of 3,4-dibromo-4-nitro-4,5-dihydrobenzo[6]-thiophen-5-one (Section VI, 1,4) in benzene, 3-bromobenzo[6]thio-phene-4,5-quinone is obtained.497 The unstable product readily condenses with ethyl cyanoacetate in the presence of base to give 3-bromo-7-(carbethoxy cyanomethyl)benzo[6]thiophene-4,5-quinone. The 4-bromo-4-nitro-4,5-dihydrobenzo[6]thiophen-5-ones prepared by nitration of 3,4-dibromo-,152,421 4,6-dibromo-,152 3,4,6-tri-bromo-,421 and 2,3,4,6-tetrabromo-5-hydroxybenzo[6]thiophene421 decompose similarly to the corresponding 4,5-quinones on being boiled in benzene. 

Carbonation of the lithium derivative of 2-methoxybenzo[6]thio-phene affords the corresponding 3-carboxylic acid.183 2-Methylbenzo-[6]thiophene-3-carboxylic acid has been obtained (45%) by carbonation of 2-benzo[6]thienylmethylmagnesium chloride (Section VI,D, 4).528 re-Butyllithium reacts selectively with the bromine atom in 3-bromo-2-fluorobenzo[b]thiophene to give a product, which on carbonation affords 2-fluorobenzo[6]thiophene-3-carboxylic acid.482 Benzo[6]thiophene-7-carboxylic acid is obtained by reduction of the corresponding thioindoxyl with amalgamated zinc and acetic acid.315 Benzo[6]thiophene-3-carboxylic acid and its 2-ethyl derivative have been prepared in high yield by treatment of the pyridinium salt of the 3-chloroacetyl derivative with alkali.132... 

The allyl glycoside of a-D-Abe-(l ->3)-a-D-Man 115 was prepared by a different approach.200 The ethyl 1-thio-D-abequopyranoside donor 113 was obtained from methyl (3-D-galactopyranoside derivative 110 according to Scheme 33. The cyclic sulfate intermediate 111 was the precursor for the stereoselective reduction with tetrabutylammonium borohydride to 112 which was further derivatized to the thioglycosyl donor 113. Donor 113 was reacted with acceptor 114 to give 115 after deprotection. 

The disaccharide epitope a-Tyv-(l —>3)-a-o- Man present in the D1 Salmonella serotype was synthesized as the pentenyl glycoside. The tyvelose donor 138 was prepared from ethyl l-thio-p-o-mannopyranoside 137 employing a single dideoxygenation step (Scheme 40). Glycosylation of 138 with the mannopyranosyl... 

The thioglycoside derivative of 4,6-dideoxy-i-/vA o-hexopyranose 160, useful as glycosyl donor has been prepared starting from the ethyl 1-thio-a-L-rhamnopyranoside (159, Scheme 46). 

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