O-acetylated

The phenolic hydroxyl group of tyrosine, the imidazole moiety of histidine, and the amide groups of asparagine and glutamine are often not protected in peptide synthesis, since it is usually unnecessary. The protection of the hydroxyl group in serine and threonine (O-acetylation or O-benzylation) is not needed in the azide condensation procedure but may become important when other activation methods are used. 

B) palladium(0)-catalyzed direct amination of the O-acetylated allylic alcohol. 

Under conditions, the reaction of tetra-o-acetyl-o-glucopyranosyl bromide with A-4-thiazoline-2-thione provides the glycosylamine (76) (N-alkylation) (Scheme 36) (163). However, treatment of 5-... 

Alkoxythiazoles are prepared by heterocyclization (274, 462). The Williamson method using catalytic amounts of KI and cupric oxide is also possible (278. 288, 306). 5-Acetoxy-4-alkenylthiazoles are obtained by treatment of 242 with acetyl chloride and triethylamine or with acetic anhydride and pyridine (450). Similarly, the reaction of diphenylketene with 242 affords 5-acyloxy-4-alkenylthiazoles (243) (Scheme 120) (450). The readiness of these o-acetylations suggests that 4-alkylidene thiazoline-5-one might be in equilibrium with 4-alkenyl-5-hydroxythiazoles (450). 

Tetra-O-acetyl-l-thio-beta-d-glucopyranosato-S )-(triethylphosphine)gold [34031-32-8]... 

Plasmid-mediated bacterial inactivation of chloramphenicol and thiamphenicol can potentially lead to three products, the 3- 0-acetyl (3), 1-0-acetyl (4), and 1,3-di-O-acetyl (5) derivatives as shown in Figure 1. 

Cinnolin-3(2//)-one (7) is methylated with diazomethane or methyl sulfate to give 2-methylcinnolin-3(2H)-one. In a similar manner, benzylation with benzyl chloride, cyanoethylation with acrylonitrile in the presence of benzyltrimethylammonium hydroxide and glucosidation with tetra-O-acetyl-a-o-glucopyranosyl bromide in the presence of a base affords the corresponding 2-substituted cinnolin-3(2//)-ones. However, glucosidation of the silver salt of cinnolin-3(2//)-one produces the corresponding O-substituted compound. 

Hydroxythiophene also exists mainly in ketonic forms. Electrophilic reagents react either at oxygen or at C-5. O-Methyl and O-acetyl derivatives are obtained in alkaline solution, probably through intermediacy of the anion. In acidic solution, coupling with benzenediazonium ion, a characteristic phenolic reaction, is found to take place (Scheme 72). 

In the case of indazoles the reaction of indazole, 5-nitroindazole or 6-nitroindazole with glycosyl halides and mercury(n) cyanide gives exclusively 2-glycosylindazoles (670), (673) and (675) (7QJHC1435). Similarly, the reaction of 1-trimethylsilyl derivatives of indazole, 3-cyanoindazole, 4-nitroindazole, 5-nitroindazole and 6-nitroindazole with 2,3,5-tri-O-acetyl-D-ribofuranosyl bromide gives only, or preferentially, the 2-ribofuranosyl derivatives (670)-(674) 7QJHC117, 70JHC1329). 

Dissolve in H2O by adding Et3N to form the salt and while hot acidify, cool and pour into a large volume of H2O. Filter off the solid, wash with H2O, dry over P2O5 in vacuum. [Nefken And Teser J Am Chem Soc 83 1263 1961 Fieser 1 485 1976 Nefkens et al. Reel Trav Chim Payx-Bas 81 683 1962] The O-acetyl derivative has m 178-180° (from EtOH). 

O-Acetyl-p-methylcholine chloride [Methacholine chloride, Amechol, Provocholine, 2-acetoxypropyl-ammonium chloride] [62-51-1] M 195.7, m 170-173", 172-173". It forms white hygroscopic needles from Et20 and is soluble in H2O, EtOH and CHCI3. It decomposes readily in alkaline solns and slowly in H2O. It should be handled and stored in a dry atmosphere. The bromide is less... 

Equilibrium constant not known in solution ctystalline form has all chlorines axial. TH-O-acetyl-p-D-xylopyranosyl chloride... 

Bis(tnfluoromethyl)-4,5-dihydrooxazin-6-ones [28] and their O-acetylated dcnvatives [96] are formed on treatment of acyl imines with acetyl chloride-hiethylamine at room temperature. The reaction was interpreted as a cycloaddition reaction involving a ketene [28] However, the periselectivity and regiochemistry of this reactwn-are not in agreement with results obtained from the reaction of... 

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