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P-Thiolactones

These reactions, first described by Staudinger, have received little attention. A more recent investigation shows that the C -S bond of the thiones regioselectively adds across the C—C bond of the ketenes (equation 11) to form 2-thietanones (p-thiolactones). Primary adducts have been isolated only in a few cases. Most often they spontaneously decompose to yield an ene and COS (equation 12). [Pg.89]

Finally, it should be mentioned that y- and 8-thiol lactones are in many cases formed simply by heating the corresponding mercaptocarboxylic acids or by treating them with phosphorus pentoxide. The P-thiolactone (20) has also been obtained by flash pyrolysis of 3-mercapto-2-naphthoic acid (equation IS). - ... [Pg.440]

The chemistry and biology of P-thiolactones 13JSC104. Chemodosimeters An approach for detection and estimation of biologically and medically relevant metal ions, anions, and thiols 12CCR 1992. [Pg.244]

Thietanones (p-thiolactones) have been obtained by hydrolysis of 2,2-dichlorothietans, by photolysis of diketone (144) or thiacyclohexanone... [Pg.116]

Sakamoto, M., Yoshiaki, M., Takahashi, M., Fujita, T, and Watanabe, S., Photochemical synthesis of tricychc P-lactams and their isomerization to P-thiolactones /. Chem. Soc., Perkin Trans. 1, 2938,1994. [Pg.2187]

Thiirane 1,1-dioxides extrude sulfur dioxide readily (70S393) at temperatures usually in the range 50-100 °C, although some, such as c/s-2,3-diphenylthiirane 1,1-dioxide or 2-p-nitrophenylthiirane 1,1-dioxide, lose sulfur dioxide at room temperature. The extrusion is usually stereospeciflc (Scheme 10) and a concerted, non-linear chelotropic expulsion of sulfur dioxide or a singlet diradical mechanism in which loss of sulfur dioxide occurs faster than bond rotation may be involved. The latter mechanism is likely for episulfones with substituents which can stabilize the intermediate diradical. The Ramberg-Backlund reaction (B-77MI50600) in which a-halosulfones are converted to alkenes in the presence of base, involves formation of an episulfone from which sulfur dioxide is removed either thermally or by base (Scheme 11). A similar conversion of a,a -dihalosulfones to alkenes is effected by triphenylphosphine. Thermolysis of a-thiolactone (5) results in loss of carbon monoxide rather than sulfur (Scheme 12). [Pg.141]

Figure 22.7 Homocysteine formation from methionine and formation of thiolactone from homocysteine. The homocysteine concentration depends upon a balance between the activities of homocysteine methyltransferase (methionine synthase) and cystathionine p-synthase. Both these enzymes require vitamin B12, so a deficiency can lead to an increase in the plasma level of homocysteine. (For details of these reactions, see Chapter 15.) Homocysteine oxidises spontaneously to form thiolactone, which can damage cell membrane. Figure 22.7 Homocysteine formation from methionine and formation of thiolactone from homocysteine. The homocysteine concentration depends upon a balance between the activities of homocysteine methyltransferase (methionine synthase) and cystathionine p-synthase. Both these enzymes require vitamin B12, so a deficiency can lead to an increase in the plasma level of homocysteine. (For details of these reactions, see Chapter 15.) Homocysteine oxidises spontaneously to form thiolactone, which can damage cell membrane.
Carboxy terminal amino acid or peptide thiols are prepared from various p-amino alcohols by conversion into a thioacetate (R2NHCHR1CH2SAc) via a tosylate followed by saponification.Several methods have been used to prepare N-terminal peptide thiols, the most common procedure is the coupling of (acetylsulfanyl)- or (benzoylsulfanyl)alkanoic acids or add chlorides with a-amino esters or peptide esters, followed by deprotection of the sulfanyl and carboxy groups. 8 16 Other synthetic methods include deprotection of (trit-ylsulfanyl)alkanoyl peptides, 1718 alkaline treatment of the thiolactones from protected a-sulfanyl acids, 19 and preparation of P-sulfanylamides (HSCH2CHR1NHCOR2, retro-thior-phan derivatives) from N-protected amino acids by reaction of P-amine disulfides with carboxylic acid derivatives, followed by reduction. 20,21 In many cases, the amino acid or peptide thiols are synthesized as the disulfides and reduced to the corresponding thiols by the addition of dithiothreitol prior to use. [Pg.304]

Similar absolute asymmetric synthesis was demonstrated in the solid-state photoreaction of A-(P,y-unsaturated carbonyl)thiocarbamate 41. [27] Achiral 0-methyl AT-(2.2-dmeth ibut-3-enoyl)-iV-phenylthiocarbarnate 41 crystallized in chiral space group P2i, and irradiation of these crystals gave optically active thiolactone in 10-31% ee. A plausible mechanism for the formation of 42 is rationalized on the basis that photolysis of 41 undergoes [2 + 2] cyclization to thietane and is subsequently followed by rearrangement to thiolactone 42. [Pg.114]

As already mentioned (Section 2.1), the preparation of p-D-gulo- and P-D-allo-configured carbapyranosyl thiols 273 and 274 utilized thiolactone 269 as an advanced chiral scaffold. Approaching the decisive annulation step, which creates the carbapyranose ring, the required aldehyde 270 was implemented from 269 via silylation and Swem oxidation. [Pg.489]

The dihydro compounds behave as typical thiolactones and are easily ring-opened with base. The 3-benzoyl-3,4-dihydrothiocoumarin (53, see p. 125) becomes, on ring opening, a useful intermediate to other systems (Scheme... [Pg.133]

The reaction was thoroughly investigated and was found to take place through initial cyclization to trana-isomer, trans- followed by epimerization to the desired c/s-thiolactone 8. The reaction was tested using DCC under various acid-base catalyses. While the use of Boden s catalyst [96] employing 4-JV,iV -dimethylaminopyridine hydrochloride (DMAP HCl) provided 8 in 63% yield, the use of more acidic pyridinium p-toluenesulfonate (PPTS) afforded a much better yield (87%) (Table 10, Entries 2 and 3). Finally, when TFA and pyridine were employed as the additives and a two-step procedure involving initial cyclization to frUFrt5-isomer trans-% at lO C followed by epimerization at 60°C, was conducted, the compound 8 was obtained in 93% yield (Table 10, Entry 4). [Pg.295]

Shapiro, G., Floersheim, P, Boelsterli, J., Amstutz, R., Bolliger, G., Gammenthaler, H., Gmelin, G., Supavilai, P, Walkinshaw, M. Muscarinic activity of the thiolactone, lactam, lactol, and thiolactol analogues of pilocarpine and a hypothetical model for the binding of agonists to the mj receptor. J. Med. Chem. 1992, 35, 15-27. [Pg.337]

The 4,5-threo-thiobutenolide 91 thus obtained was then reduced and shortened by one carbon atom to arrive at aldehyde 92 onto which a highly stereoselective cyclopentane-forming annulation was performed via a TBSOTf/DIPEA-promoted silylative protocol. In the event, a major 2,3-cA-configured bicycle educt 94 was isolated in a 82% yield, accompanied by only 7% of 7ra 5-isomer 93. Completion of the synthesis entailed the reductive cleavage of the thiolactone bond within 93 and 94, followed by acidic deprotection, giving l-deoxy-l-thio-4a-carba-P-D-... [Pg.465]

Poly(8-mercapto acids). 8-Thiovalerolactone was polymerized in 21% yield to a linear poly(thiol ester)—UJ chci. = 14.7 ml/gram, m.p. 117°-118°C (17). The molecular weight of the polymer seems to be controlled by the monomer-polymer equilibrium. The same product (XXII) was obtained by distilling thiol-4-pentenoic acid (XXI) (19), giving the thiolactone (XXIII) as a by-product. [Pg.122]

The photochemistry of monocyclic a,p-unsaturated thiolactones has only been investigated recently. One reason for this is that the first syntheses of 2(5//)-thiophenones from thiophenes were only developed in the late 1960s and early 1970s and that the first report on a 5,6-dihydrothiin-2-one was published even later [60]. [Pg.95]


See other pages where P-Thiolactones is mentioned: [Pg.50]    [Pg.349]    [Pg.104]    [Pg.273]    [Pg.2176]    [Pg.50]    [Pg.349]    [Pg.104]    [Pg.273]    [Pg.2176]    [Pg.212]    [Pg.319]    [Pg.133]    [Pg.887]    [Pg.393]    [Pg.321]    [Pg.322]    [Pg.887]    [Pg.25]    [Pg.308]    [Pg.393]    [Pg.548]    [Pg.11]    [Pg.428]    [Pg.270]    [Pg.413]    [Pg.212]   
See also in sourсe #XX -- [ Pg.104 , Pg.104 ]




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