2- ethyl phosphates protect phosphate groups

DBU, CH3CN, 140 s. The 2-(4-nitrophenyl)ethyl (Npe) phosphate protective group and the 2-(4-nitrophenyl)ethoxycarbonyl (Npeoc) group are stable to these conditions, but the cyanoethyl group is not. 

NH4OH, MeOH. These conditions result in cleavage of only one ethyl group of a diethyl phosphonate. Selective monodeprotection of a number of alkyl-protected phosphates is fairly general for cases where cleavage occurs by the release of phosphate or phosphonate anions. 

Introduction of a phosphate monoester and removal of its protecting groups was a serious impediment in a synthesis of the serine-threonine phosphatase inhibitor Calyculin A by Evans and co-workers [Scheme 7,22].38 The four phosphate protecting groups evaluated were 2-cyanoethyl and 2-(trimethylsi]y])ethyl (see below), benzyl and p-methoxybenzyl. Of these, the p-methoxybenzyl phosphate ester offered the best compromise between base stability (it survived a Wittig reaction in the presence of a metal amide base) and acid lability required for the final deprotection step in which three secondary terf-butyldimethylsiiyl... 

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... 

The 2-(methylsulfonyl)ethyl group 5 together with its fert-butyl-,86 phenyl-87 and benzyl-substituted88 relatives, comprise a small group of phosphate protecting groups that cleave with mild bases such as triethylamine. The van Boom... 

---