Intermediates in isoprenoid biosynthesis

The first intermediate in the nonmevalonate biosynthetic pathway to isoprenoids is the formation of DXP. DXP and/or Dxose are intermediates in vitamin B ₁ and B₆ biosynthesis. DXP and Dxose were synthesized from isopropylidene-D-threitol in 8 and 5 steps, respectively. Once synthesized, DXP and Dxose were used to confirm the identity of DXPSase products. As a result, it was found that DXPSase was able to synthesize DXP only at a higher pH than it makes Dxose. The synthesis of DXP and Dxose in combination with the product analysis helped to develop an enzymatic assay for DXPSase activity.; The first committed step in isoprenoid biosynthesis via the nonmevalonate pathway appears to be the formation of MEP. However, no intermediates or enzymes have been identified between MEP and either DMAPP or IPP. A synthetic library representing 28 potential intermediates between MEP and either DMAPP or IPP formation were synthesized. Utilizing the procedure utilized by Seto, the compounds were tested for the ability to rescue a DXPSase knockout strain in E. coli. None of the potential intermediates were Able to rescue the knockout strain. However, the intermediates will prove valuable for the identification of compounds isolated from the nonmevalonate pathway in later experiments.; The first committed enzyme in cholesterol biosynthesis is SQSase. The rearrangement of PSPP to squalene, has been highly debated for decades. In a SQSase catalyzed solvolysis of PSPP reaction in the presence of a nonredox active analog of NADPH, NADPH₃, a tertiary cycloproplcarbinol was isolated. The absolute configuration of this compound was identified by two independent syntheses. The absolute configuration was assigned to be that of the R,R,S configuration indicative of the solvolytic capture of a tertiary cyclopropylcarbinyl cation. The results suggest that the normal SQSase catalyzed reaction of PSPP to squalene proceeds through a nonclassical cyclopropylcarbinyl-cyclopropylcarbinyl rearrangement to form a tertiary cyclopropylcarbinyl which is ultimately reduced with NADPH to form squalene.