Acetyl derivatives s. Acylation

Acylation of pyridazinethiones with acetyl chloride or benzoyl chloride gives the corresponding S-acylated products. 6-Mercaptopyridazine-3(2//)-thione gives either mono- or di-S-acylated products. A bispyridazinyl derivative is formed when phosgene or thiophos-gene is used as acylating agent. 

The tetrahydro-l,3-oxazines which contain a free A -hydrogen atom can be iV-acylated and A -nitrosated. - Certain A-substituted derivatives of tetrahydro-l,3-oxazin s can also react with acetic anhydride to form A -acetyl derivatives. > Most tetrahydro-l,3-oxazines add methyl iodide to form quaternary... 

Corey and Ishihara s synthesis of phe-box ligand 29 began with the trifluoro-acetyl derivative of (5)-phenylglycine 26. Treatment of 26 with methylmagnesium iodide, as shown in Figure 9.7, followed by potassium hydroxide in methanol afforded amino alcohol 27 in 88% yield (2 steps).This was then acylated with dimethylmalonyl dichloride 24 and triethylamine followed by cyclization using methanesulfonic acid at reflux to afford phe-box ligand 29 in 78% yield. 

The S-CoA derivative then acylates the amino group of the particular amino acid in an analogous way to the acetylation of amine groups described above, yielding a peptide conjugate. This is catalyzed by an amino acid N-acyltransferase, which is located in the mitochondria. Two such enzymes have been purified, each using a different group of CoA derivatives. 

Deracemization of mandelic add with the combined action of two enzymes has been reported. rac-MandeUc acid is acylated by a Pseudomonas sp. lipase in diisopropyl ether. After solvent removal the mfacture of mandeUc acid enriched in the R-form and the 0-acetyl derivative of the S-configuration are subjected to the mandelate racemase-catalyzed racemization in aqueous buffer. In these conditions only the non-acetylated hydroxy acid is racemized. In order to obtain (S)-0-acetylmandelic acid in an 80% isolated yield and a >98% e.e. the process must be repeated four times [9]. 

An analysis of several derivatives of types 199a,b and 202a,b reveal that the 5-proton appears in that S 7.45-7.75 region. As expected, the introduction of an acyl group at position 4 of such compounds causes a significant deshielding of the 5-proton thus that of 18a absorbs at 5 7.61 and that of the JV-acetyl derivative 18d at d 8.14. ... 

Photolysis of 3-acyltetrahydro-l,3-thiazine-2-thiones (165) initially gives 5,6-dihydro-4i/-l,3-thiazine-2-thiol (166) and ketenes (167), but these products immediately recombine to form cephem thiols (168) as the major products (Scheme 30). Although the cephem thiols are unstable, they may be isolated as their S-acetyl derivatives (169) if acetyl chloride and triethylamine are added to the reaction mixture, prior to irradiation with light. The A-acetylperhydrothione (170) is also formed as a by-product, and this provides evidence for the suggested pathway since it probably arises through acylation of the intermediate thiol (166) (Scheme 30) <86TL1335>. 

Acyl derivatives are formed in a reaction of 3H-pyrrolizine (1) with dichloroketene ketones (23) were formed depending on the conditions used. Ketones (23b) and (23c) could be obtained in good yields from (1) and the appropriate acid chloride in ether in the presence of anhydrous potassium carbonate, but the 2-acetyl derivative (23a) could not be obtained in this way <82JCR(S)54>. 

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