Syntheses of coenzyme Q(3-8) are described, as well as related systems such as plastoquinone-5. Preparation of thr higher homologues of the ubiquinones relies on two new conjunctive reagents, or "linchpins", each of which ultimately corresponds to two or three prenyl units. These allow for attachment of a polyprenyl halide at one end, followed by a Ni(0)-catalyzed cross-coupling at the other terminus with a chloromethylated p-quinone.
Inhibition of IspH, a [4Fe–4S]2+ Enzyme Involved in the Biosynthesis of Isoprenoids via the Methylerythritol Phosphate Pathway
摘要:
The MEP pathway, which is absent in animals but present in most pathogenic bacteria, in the parasite responsible for malaria and in plant plastids, is a target for the development of antimicrobial drugs. IspH, an oxygen-sensitive [4Fe-4S] enzyme, catalyzes the last step of this pathway and converts (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMBPP) into the two isoprenoid precursors: isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). A crucial step in the mechanism of this enzyme is the binding of the C4 hydroxyl of HMBPP to the unique fourth iron site in the [4Fe-4S](2+) moiety. Here, we report the synthesis and the kinetic investigations of two new extremely potent inhibitors of E. coli IspH where the OH group of HMBPP is replaced by an amino and a thiol group. (E)-4-Mercapto-3-methylbut-2-en-1-yl diphosphate is a reversible tight-binding inhibitor of IspH with K-i = 20 +/- 2, nM. A detailed kinetic analysis revealed that (E)-4-amino-3-methylbut-2-en-1-yl diphosphate is a reversible slow-binding inhibitor of IspH with K-i = 54 +/- 19 nM. The slow binding behavior of this inhibitor is best described by a one-step mechanism with the slow step consisting of the formation of the enzyme-inhibitor (EI) complex.
THE ASYMMETRIC DIELS–ALDER REACTIONS OF α,β-UNSATURATED CARBOXYLIC AMIDES DERIVED FROM (−)-PHENYLGLYCINOL AND THE ASYMMETRIC TOTAL SYNTHESIS OF (+)-FARNESIFEROL C
作者:Teruaki Mukaiyama、Nobuharu Iwasawa
DOI:10.1246/cl.1981.29
日期:1981.1.5
The asymmetric intramolecular Diels–Alderreactions of α,β-unsaturated carboxylic amides derivedfrom (−)-phenylglycinol were studied and successfully applied to the asymmetric total synthesis of (+)-farnesiferol C.
研究了衍生自 (-)-苯基甘氨醇的 α,β-不饱和羧酸酰胺的不对称分子内 Diels-Alder 反应,并成功应用于 (+)-farnesiferol C 的不对称全合成。