Dibenzylphosphoric acid

Reaction of aziridine peptides 139 (Scheme 3.50) and dibenzylphosphoric acid... 

Replacement of H in H3PO4 by a radical R gives substituted phosphoric acids 0P(0H)20R and OP(OH)(OR)2 and finally the phosphoric ester, OP(OR)3. The structure of dibenzylphosphoric acid, HP02(0CH2C6Hs)2, was described in Chapter 8 the molecules are linked in pairs by O-H-0 bonds as in dimers of carboxylic acids. Examples of mono- and di-substituted ions are the phenyl-phosphate ion, (h), studied in the K salt, and the diethylphosphate ion, (i), in the Ba salt, and of an ester, triphenylphosphate,... 

The reason for the low reactivity of dibenzyl phosphate is that it cannot expel benzyl alcohol to form metaphosphate. Therefore, the solvolysis must proceed by nucleophilic attack of hydroxide on the dibenzyl phosphate monoanion or attack of water on the neutral, acidic dibenzylphosphoric acid. 

Dibenzylphosphoric acid and dicyclohexylcarbodi-imide were used to generate tetrabenzyl phosphate. This could then be reacted with 2,3-isopropylidene-glycerol in the presence of imidazole to yield 2,3-iso-propylidene-5n-glycerol-l-dibenzyl phosphate. De-benzylation of the latter was carried out with barium iodide and the barium salt was converted to the silver salt which was reacted with 3-iododeoxy-l-oleoyl-2-palmitoyl-5n-glycerol. The fully protected phosphatidylglycerol was debenzylated, followed by reaction with boric acid in trimethyl borate which effected removal of the isopropylidene group (Rosenthal, 1975). Yields of 30% are obtained (Slotboom and Bonsen, 1970). 

Rosenthal (1975) provides notes on certain parts of the preparative procedure. This includes preparation of dibenzylphosphoric acid and of 2,3-isopropylidene-5n-glycerol. 

Other reagents that open the epoxide ring with substitution, to give the useful derivatives indicated in parentheses, include phenols (phenyl ethers) (81) y carboxylic acids (esters) (8 ), hydrogen sulfide in the presence of barium hydroxide (thiols) (82), sodium methyl mercaptide (methyl thio-ethers) (83), dipotassium hydrogen phosphate or dibenzylphosphoric acid (phosphate esters) (84), alkyl or aryl magnesium halides (halodeoxysugars)... 

Disubstituted phosphoric acids, HP0j(0R)2, provide examples of both dimers and chains exactly comparable with the two types of HSO4 ions, and infinite chains also occur in crystalline benzene seleninic acid. The dimer in dibenzylphosphoric... 

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