Protecting groups selective removal

Mercuric acetate/formic acid Benzylthiomethyl as S-protective group Selective removal of the protective group... 

Hydrogen chloride (s. a. under H2O2) Dibenzosuberyl as protective group Selective removal... 

Peptide synthesis requires the use of selective protecting groups. An N-protected amino acid with a free carboxyl group is coupled to an O-protected amino acid with a free amino group in the presence of dicydohexvlcarbodi-imide (DCC). Amide formation occurs, the protecting groups are removed, and the sequence is repeated. Amines are usually protected as their teit-butoxy-carbonyl (Boc) derivatives, and acids are protected as esters. This synthetic sequence is often carried out by the Merrifield solid-phase method, in which the peptide is esterified to an insoluble polymeric support. 

In a recent application of this strategy, nitrocyclohexane 143 (prepared from nitrosugar 142 by intramolecular Henry reaction) was subjected to a radical denitration by HSnBu3, after protection of the hydroxyl groups to avoid side reactions. Inositol 146 was selectively obtained in good yield, once the hydroxyl protecting groups were removed (Scheme 45).101... 

There is one example in which an ethoxyethyl (EE) protecting group is removed from a phenol during a Mukaiyama oxidation. According to the authors, this deprotection is promoted by a selective complexation of one oxygen with a magnesium atom.80... 

With the spirocycle in hand, a regioselective and stereoselective Heck reaction was used to install the substituted aromatic portion of the molecule (Scheme 28.5). It is interesting that the addition of water to the reaction provided the high selectivity. The remaining olefin was reduced over Pearlman s catalyst, and the protecting groups were removed to provide the desired NK-1 antagonist 14 in 7 overall steps.33... 

The 2-(methyldiphenylsilyl)ethyl (DPSME) group was used to protect a phosphate in a synthesis of Lysobisphosphatidic Acid [Scheme 7.40].82 The phosphate protection was introduced by a phosphite triester approach to give the symmetrical phosphate 40 2. The two isopropylidene groups were removed by acid hydrolysis without harm to the phosphate and the resultant diols selectively protected on their less hindered termini with fert-butyldiphenylsilyl groups. Acylation of the remaining secondary hydroxyls with oleic anhydride afforded the diester 403, whereupon the silyl protecting groups were removed with... 

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