2- methyl ester protect phosphate groups

A d(5 -CCGp)—the 5 end of the trinucleotide is protected as the methyl ester, while the 3 end carries a phosphate group activated by the condensation... 

The 2-(acetoxymethyl)benzoyl-protective group (4,5,6) has initially been used in the synthesis of particularly base-labile backbone modifications, such as phosphate methyl esters or methylphosphonates [51, 52], again thymine remains unprotected. Cleavage is achieved by elegant intramolecular reaction within 90 min at room temperature by use of potassium carbonate in dry methanol (Fig. 11). 

The rapid aminolysis of cobalt(llI)-chelated glycine esters in aprotic solvents (Scheme 10 N4 = (en)2 or trien, R = Me, Et, R = H, CHR"C02Et) could be of value in peptide synthesis. The cobalt atom acts as both an N-protecting and an activating group. The synthesis of the chelated amino acid esters has presented some difficulties.207 A recent paper208 describes the use of methyl trifluoromethanesulfonate for the alkylation of chelated amino acids using dry trimethyl phosphate... 

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