Sulphur, replacing oxygen

The sulphur analogues of the glycols, i.e., thio-glycols, or di-valent mercaptans are definitely known compounds. Furthermore, it is found, that when sulphur replaces oxygen, in compounds of this class, two sulph-hydrogen groups (—SH), may be linked to one carbon atom and a stable compound result. 

Since sulphur is in the same group as oxygen in the periodic table it replaces oxygen in organic structures to produce thio analogues such as ... 

Additional BHT-derived 5-LO inhibitors bear heteroatom-linked 4-substituents. Searle s SC-45662 (50) was selective (25 1) for 5-LO over CO in cRBL (3.7 /iM) and in A23187-stimulated RBL-1 cells (7.1 yuM) [146]. Besides NSAID-like activity in RAA (down to 10 mg/kg p.o.), SC-45662 also inhibited GPB (ED30 16.7 mg/kg p.o.), and LTB4 release from ulcerative colitis rectal mucosal biopsy samples was decreased [147]. Several patents have described similar compounds where the alkyl substituent on sulphur is varied quite widely [148 151]. Oxidation of the distal sulphur was consistent with activity, while replacement of this sulphur with oxygen gave reduced potency. Simple alkyl groups, alkylene-linked esters and amides, and disulphide-linked alkanoic esters were also active in cRBL with similar potency free carboxylic acids were somewhat less potent. Oxidation of the sulphur attached to the phenolic ring destroyed the activity. 

Naively, one would expect the effect of replacing oxygen by sulphur to be similar to the effect of replacing oxygen by nitrogen, but, experimentally, the effects are far from clear-cut. Mario Pinto et al. (1985) indeed showed that the conformational equilibrium of [61] showed the effect on the nature of R... 

Synthetic and biological evaluations of new diadenosine polyphosphate (175) analogues on blood platelet aggregation have been reported. The most active are compounds with sulphur replacing one or both non-bridging oxygens at... 

Thio-ureas.—As sulphur may replace oxygen in carbon dioxide, alcohol, carbonyl chloride and ammonium cyanate yielding corresponding thio compoundsj so also there are sulphur analogues of urea known as thio-ureas. These need not be considered more than to give the oxygen and sulphur compounds in this relationship. 

Replacement of sulphur by oxygen is known to occur in a number of cases, and the oxy... 

The relative effect of oxygen and sulphur is shown in the constants for glycollie acid and thioglycolhc acid. When sulphur replaces the oxygen of the hydroxyl group it has a marked effect on the constant of an acid the constant for thioacetic acid, CH3.CO.SH is 0.469 while that of acetic acid is. 0018... 

Replacing oxygen donor atoms with increasing numbers of nitrogens has the effect of decreasing stability constants for alkali and alkaline earth metal cations whilst increasing those of transition metal cations (54,55). More pronounced effects occur with sulphur-containing cryptands (56,57). 

Thioacids are acids derived by replacing oxygen by sulphur, and are named by adding thio- before the trivial name of the acid andseleno- and telluro-acids are treated similarly. Examples are H2S2O2 thio-sulphurous acid H2S2O3 thiosulphuric acid KSCN... 

The final products are then sulphuric acid, nitrogen oxide and oxygen the two latter react and the cycle goes on. Theoretically therefore, the nitrous fumes are never used up. In practice, however, some slight replacement is needed and this is achieved by adding a little concentrated nitric acid to the mixture in the Glover tower ... 

A study of the chlorine oxidation of 2-hydroxyethyl octyl sulphoxide92 (equation 28) showed that a cyclic intermediate is probably involved in the process which gives the sulphone in good yield. Labelling studies have shown that the hydroxyl group is replaced by a chlorine atom whilst the hydroxyl oxygen atom is transferred to the sulphur atom. A similar result was obtained for 3-hydroxypropyl and 4-hydroxybutyl alkyl sulphoxides93. 

Replacement of the anomeric oxygen with a sulphur atom 5-glycosides... 

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