Pyridyl disulphides

A. Synthetic Methods.—There have been no strikingly new approaches to the general problem of phosphorylation, but several ingenious methods of preparing suitable active esters under mild conditions have been reported. Typical of these is the reactive intermediate (1) formed from reaction of a mono- or di-ester of phosphoric acid with (2), itself produced by reaction of triphenylphosphine with bis(2-pyridyl) disulphide (preferably in the presence of mercuric ion as scavenger for the 2-mercaptopyridine liberated). 

The use of the triphenylphosphine-di(2-pyridyl) disulphide reagent for effecting condensation reactions has been reviewed.84 Combination of triphenylphosphine with bis(O-thiocarbonyl) disulphide gives a superior reagent compared to that mentioned above for the preparation of mixed diesters of phosphoric acid from monophosphate esters.86... 

The bicyclic lactone (117) has been considered as a useful synthon for the synthesis of verrucarol (118). A second synthesis of this lactone has been described (Scheme 22)7° Starting from verrucarol (118), Tamm et have appended the two requisite side-chains (119) which can be lactonized with di-(2-pyridyl) disulphide and triphenylphosphine to give tetrahydroverrucarin J (120). A recent investigation of the biosynthesis of trichodermin (121) using [l- C]acetate is in accord with an earlier result although some reassignments of certain chemical shifts have been suggested, ... 

The application of tertiary phosphines as co-reagents in dehydration reactions leading to the synthesis of peptides and nucleotides has been reviewed. The tri-phenylphosphine-di-2-pyridyl disulphide combination, previously used as a condensing agent for peptide synthesis, has been modified by employing an insoluble, polymeric, triarylphosphine, enabling a convenient filtration procedure for separation of the products to be used. ... 

Corey s general method of electrostatically-driven cyclization of hydroxy-acids to medium and large rings has been applied to a new synthesis of vertaline (32). The hydroxy-acid (35), obtained by hydrolysis of natural vertaline, was converted into vertaline by reaction with 2-pyridyl disulphide and triphenylphosphine. Even on a small scale the yield was 67%, and clearly this will be an invaluable cyclization procedure in the synthesis of lythraceous alkaloids. 

Thiol containing peptides 8. OTHERS Glutathione-2-pyridyl disulphide Activated thiol-Sepharose 4B 38... 

Phosphorylation procedures using activated phosphate esters continue to be developed and esters of the type (3) may be conveniently prepared from monoalkyl phosphates and imidazole (or 2-hydroxypyridine) using bis-(2-pyridyl) disulphide and triphenylphosphine. -Nitrophenyl phosphate (4) and its symmetrical pyrophosphate (5) have been found to phosphorylate alcohols in the presence of pyridine and it is probable that... 

A mixed disulphide derivative of agarose, agarose-glutathione-2(5-nitro-pyridyl)-disulphide, has been used to immobilize bovine galactosyltrans-ferase. As the immobilized enzyme retains biosynthetic activity, the thiol group of the enzyme that is involved in the coupling must be physically distinct... 

Di-(2-pyridyl) disulphide has found a novel use as oxidant in peptide synthesis iV-benzoyl-L-leucine is coupled to glycine ethyl ester to give the protected dipeptide, when triphenylphosphine and the disulphide are added, formation of triphenyl phosphite and pyridine-2(li7)-thione balancing the equation. ... 

The use of triphenylphosphine and 2,2 -bipyridyl disulphide in oxidation-reduction condensations has been extended to the phosphorylation of alcohols and phosphates, and to the preparation of 5 -(2-pyridyl) phosphorothioates (60) which have been used for the synthesis of pyrophosphates (see Chapter 6, Section 1). 

Two different methods for introducing disulphide bonds or cross-links have been reported. In the first, an aliphatic isocyanate with a pyridyl-protected... 

Under strongly basic conditions, o-bromoacetophenones and carbon disulphide react to give a high yield of a benzothiopyranone. 2-Bromo-3-pyridyl ketones react with thioesters to produce a fused thiopyranone ring. 

These compounds readily undergo the desired addition-cyclization with carbon disulphide directly in ethanol at room temperature, no condensing agent being required. A-Methylpicolinic acid amidrazone produces the expected 2-(2-pyridyl)-4-methyl-l,3,4-thiadiazoline-5-thione... 

More interestingly, electron transfer reaction of cytochrome c and other redox proteins occurs with fast rates at modified electrodes. The most efficient electrode surface promoters tend to be bifunctional molecules containing surface-active functional groups (thiol, disulphide, or pyridyl) which bind the promoter to the electrode surface and weakly basic or anionic functional groups (such as pyridyl nitrogen, carboxy-late, sulphonate or phosphate) which can bind the positively charged cytochrome c [188-190,204-211]. For instance, if a gold electrode is modified with 4,4 -bipyridine, this promoter forms a monolayer at the... 

In the heterocyclic field, sulphur substitutions include the sulphonation of quinoline to produce mainly the 8-acid, plus the 5-, 6-, and 7-acids, the chlorosulphonation of 2-(3,4-dicholorophenyl)- and 2-(3-pyridyl)-imidazole (on the imidazole ring) and of 2-(4-chlorophenyl)imidazole on both aromatic rings, the tosylation at N-3 of some 2-(monosubstituted amino)-l,3,4-thiadiazoles (which isomerise to products that are sulphonylated on the exocyclic nitrogen), and the thiolation of 2-methylindolizine with diaryl disulphides to form (53). ... 

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