Amido groups, protection

Preferential and selective cleavage of sec. amido groups Protection of carboxyl as silyl esters... 

As many natural and synthetic /3-lactams bear 3-acylamino substituents, the corresponding free amines or protected forms thereof are versatile synthetic intermediates. They may be prepared in several ways, for example by deacylation of the 7-amido group in naturally occurring penicillins by enzymic or chemical means. Chemical degradation usually involves conversion of the amide to a chloroimidate followed by cleavage with aqueous alcohols (75S547 p. 560, 78T1731 p. 1753). 

The 9-phenylfluoren-9-yl (PhFI) group is very useful for protection of the amino group. Pd/C can remove the Pf group and reduce the amido group,... 

In Pschorr reactions involving anilides, amido groups must be protected to avoid the formation of triazinones122 iV-alkylation has commonly been employed, but the resulting iV-alkylphenanthridones are difficult to dealkylate. Similarly, protection by AT-alkylation has been employed in the case of the benzylamine (104 (R = Me).138 In a procedure designed to circumvent this difficulty, the N-sulfonylated diazonium chlorides, e.g., 104a-c, are decomposed catalytically acid hydrolysis, followed by oxidation, of the 5,6-dihydro derivative... 

In the addition to protected D-glucal (Table 3) and D-allal (13), the amido group is always introduced trans to the C-3 acetoxy group. 

Starting from a carbaboranyl bisphosphonite bearing four amido groups, treatment with an excess of protected galactose (59) and BIT according to the procedure described above yielded bisphosphonate 64 and bisphosphonothioate 65 after oxidation and sulfurization, respectively. Cleavage of the isopropylidene moieties led to an equilibrium between a and P forms of the... 

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