Alkyl pyrophosphates, synthesis

Direct synthesis of P. P1-diethyl pyrophosphate 89> was accomplished later. It is stable at pH 3, but hydrolyzes rapidly at pH 7/room temperature. Thus in this case it is the dianion which hydrolyzes faster than the monoanion, in contrast to the behavior of alkyl phosphates or pyrophosphate monoesters (see below). 

The crucial intermediacy of cyclopropylcarbinyl species in the biological synthesis of hundreds (thousands) of steroids, carotenoids, retinoids and derivatives is exemplified by the C30 presqualene pyrophosphate (77) and the C40 prephytoene pyrophosphate (89). In the biosynthetic construction of the key C(l)-C(l) carbon-carbon in head-to-head joining of Cl 5 or C20 alkyl alcohol pyrophosphate esters, the cyclopropylcarbinyl strategy via a formal insertion of C(l) of one monomer into the C(2)-C(3) double bond of the second monomer appears to be the central mechanistic solution in the biochemical inventory. The cyclopropylcarbinyl pyrophosphate forms as obligate intermediate whether the final... 

Given a sufficiently strong base, the activation produced by the phosphoryl group next to an adjacent C—H bond will allow deprotonation and the generation of a highly reactive carbanion. Butyllithium has been commonly used for this purpose, but a preference has been shown in recent work for Ida. Treatment of the anion from methyl methyl(4-morpholinyl)phosphinate (284) with farnesyl chloride yields 285, which, on acidolysis, affords the phosphonic acid 286, employed in the synthesis of a pyrophosphonate analogue of farnesyl pyrophosphate ". Alkylation of the carbanion from the chiral phosphonic diamide 287 (X = Me or higher alkyl) leads to the diastereoisomeric phosphonic... 

Upon the synthesis of IPP (C5) and its isomer DMAPP (C5) by either MVA or DXP pathways, the next step is chain elongation. The carbonium ion is a potent alkylating agent that can react with IPP (three molecules of IPP converted into one molecule of geranyl diphosphate (GPP) by condensation reaction catalyzed by enzyme geranyl diphosphate synthase), to yield geranyl diphosphate (GPP). Famesyl pyrophosphate synthase (EPS) is the prenyltransferase that catalyzes l -4 condensation reactions of IPP with the allylic diphosphates, dimethylallyl diphosphate (DMAPP), to produce famesyl pyrophosphate (FPP). 

Fig. 1. Preparation steps for the synthesis of [ >-(bromoacetylpyridinio)-n-alkyl] adenosine pyrophosphates.

---