Acetyl sidechain

Typical Lewis acids such as AlCl3 and ZnCl2 display excellent catalytic activity in most Friedel-Crafts type reactions (9, 10) and are also known to catalyze coal liquefaction and solubilization (11-26). Because of this latter property, acid-catalyzed depolymerization has become a useful method for structural investigation of coal (27). The rationale for solubilization is interpreted either in terms of depolymerization via rupture of the bridges or, since the overall reaction in general is that of Friedel-Crafts alkylation or acetylation, in terms of the effect of the sidechains introduced on the aromatic ring system. 

Guanidine (arginine sidechain) Methyl groups (nonacidic) Methyl groups CH X (CH-acidic, e.g., acetyl-CoA) + CO,... 

Particularly satisfying was the ease with which 157 was homologated to 158 (92%). Reduction of the ketone carbonyl in a chemoselective manner was not possible because of the steric protection it benefits from. This potential complication was skirted when it was found that the hydroxy lactol produced by diisobutylaluminum hydride reduction responded to the Fetizon reagent only at the five-membered site to deliver 159. With the stereochemistry of 159 securely established by NOE analysis, no obstacles were encountered during acetylation and the subsequent completion of sidechain construction. 

Triflupromazine is prepared by addition of the dimethylaminopropyl sidechain to the phenothiazine nucleus (II)or its N-acetyl derivative (III) and conversion of the base to the hydrochloride (I). Diazotization of the 7-aminoanalogue (IV) also yields I. 

Tritylthioazetidinone-phosphoranes unsubstituted at C3, either racemic (from 4-acetoxyazetidinones) or optically active (from 6a-bromopenams), were key intermediates in the Bristol penem programme in fact, they proved good substrates for the introduction of the (li )-hydroxyethyl sidechain by the acetylation-reduction sequence [51a]. Hydroxyethylated argentiothioazetidin-ones 229 are no longer obtained by this way, but have retained their original... 

D-Gulonolactone has been used to prepare 1-deoxy-D-gulitol and hence 2,3,4,5-tetra-0-acetyl-6-bromo-l,6-dideoxy-D-gulitol required for the synthesis of the sidechain in the bioactive i-lactone (+)-anamarin (83). ... 

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