Phthaloyl protecting group

The syntheses of pyrimido[l,2-a]quinoline chromophore of pseudobactins are depicted in Schemes 6 and 7 (88MI4 90JOC4246). When allyloxycarbonyl and phthaloyl protective groups were used, then along with pyrimido[l,2-a]quinoline derivatives 410 and 411, tetracyclic 412, corresponding to the chromophore of azobactin, was formed (Scheme 6). Pyrimido[l,2- ]quinoline (413) was obtained in good yield when 2,2,2-... 

Addition of the lithium acetylide of tetrahydropyranyl-protected but-3-yn-l-ol 156 provided the racemic alcohol 157 (Scheme 34). The nitrogen was introduced through a Mitsunobu reaction, followed by oxidation of the primary alcohol to the carboxylic acid and a change of the phthaloyl protecting group to Boc protection. The latter reaction was necessary because hydrazinolysis of the C-terminal amide analogue of 159 did result in deeply red-colored mixtures, indicating that phthaloyl removal by this method should occur prior to peptide synthesis. 131 ... 

Cleavage of phthaloyl protective group. The phthaloyl group is not useful for protection of the amino group of penicillins and cephalosporins because hydrazinolysis (Ing-Manske procedure, 1, 442) disrupts the azetidinone ring. Eli Lilly chemists have reported a new method of dephthaloylation that overcomes this difficulty. The phthalimido compound (1) is hydrolyzed by aqueous sodium sulfide to the corresponding phthalamic acid (2), which on dehydration... 

Gabriel synthesis. The main drawback to the classical Gabriel synthesis is difficulty in cleavage of the phthaloyl protective group. The reagent (1) can serve as a substitute for potassium phthalimide. The methoxycarbonyl group is cleaved by mild alkali, and thus allows direct synthesis of r-butoxycarbonylamino acids (equation I). ... 

An improved method for the removal of the phthaloyl protecting group from penicillins and cephalosporins. 

A novel method for removing the phthaloyl protecting group from the base-sensitive penicillins and cephalosporins has been reported. The imide (192) is ring-opened with sodium sulphide, re-closed to the phthalisoimide (193), and finally cleaved by hydrazine under anhydrous conditions at low temperature to generate the free amine. 

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