Organic chemists have always been fascinated by the cyclopropane subunit.1 The smallest cycloalkane is found as a basic structural element in a wide range of naturally occurring compounds.2 Moreover, many cyclopropane-containing unnatural products have been prepared to test the bonding features of this class of highly strained cycloalkanes3 and to study enzyme mechanism or inhibition.4 Cyclopropanes have also been used as versatile synthetic intermediates in the synthesis of more functionalized cycloalkanes5,6 and acyclic compounds.7 In recent years, most of the synthetic efforts have focused on the enantioselective synthesis of cyclopropanes.8 This has remained a challenge ever since it was found that the members of the pyrethroid class of compounds were effective insecticides.9 New and more efficient methods for the preparation of these entities in enantiomerically pure form are still evolving, and this review will focus mainly on the new methods that have appeared in the literature since 1989. It will elaborate on only three types of stereoselective cyclopropanation reactions from olefins: the halomethylmetal-mediated cyclopropanation reactions (eq 1), the transition metal-catalyzed decomposition of diazo compounds (eq 2), and the nucleophilic addition-ring closure sequence (eqs 3 and 4). These three processes will be examined in the context of diastereoand enantiocontrol. In the last section of the review, other methods commonly used to make chiral, nonracemic cyclopropanes will be briefly outlined.

Stereoselective Cyclopropanation Reactions

http://hoffman.cm.utexas.edu/courses/wood_lungdahl_1.pdf

Acetogenesis and the Wood-Ljungdahl Pathway of CO2 Fixation

Asymmetric Ylide Reactions: Epoxidation, Cyclopropanation, Aziridination, Olefination, and Rearrangement

http://wolfson.huji.ac.il/purification/PDF/Literature/Arnau2006.pdf

Current strategies for the use of affinity tags and tag removal for the purification of recombinant proteins.

Thioamides as useful synthons in the synthesis of heterocycles.

The strict anaerobic, thermophi- lic bacterium Moorella thermoacetica metabolizes C1 compounds for example CO2/H2, CO, formate, and methanol into acetate via the Wood/Ljungdahl pathway. Some of the key steps in this pathway include the metabolism of the C1 compounds into the methyl group of methylenetetrahydrofolate (MTHF) and the transfer of the methyl group from MTHF to the methyl group of acetyl-CoA catalyzed by methyltransferase, corrinoid protein and CO dehydrogenase/acetyl CoA synthase. Recently, we reported the crystallization of a 25 kDa methanol- induced corrinoid protein from M. thermoacetica (Zhou et al., Acta Crystallogr F 2005; 61:537-540). In this study we analyzed the crystal structure of the 25 kDa protein and provide genetic and bio- chemical evidences supporting its role in the methanol metabolism of M. thermoacetia. The 25 kDa protein was encoded by orf1948 of contig 303 in the M. thermoacetica genome. It resembles similarity to MtaC the corrinoid protein of the methanol:CoM methyltransferase system of meth- ane producing archaea. The latter enzyme system also contains two additional enzymes MtaA and MtaB. Homologs of MtaA and MtaB were found to be encoded by orf2632 of contig 303 and orf1949 of contig 309, respectively, in the M. thermoacetica genome. The orf1948 and orf1949 were co-tran- scribed from a single polycistronic operon. Metal analysis and spectroscopic data confirmed the presence of cobalt and the corrinoid in the puri- fied 25 kDa protein. High resolution X-ray crystal structure of the purified 25 kDa protein revealed corrinoid as methylcobalamin with the imidazole of histidine as the a-axial ligand replacing benzii- midazole, suggesting base-off configuration for the corrinoid. Methanol significantly activated the expression of the 25 kDa protein. Cyanide and nitrate inhibited methanol metabolism and sup- pressed the level of the 25 kDa protein. The results suggest a role of the 25 kDa protein in the methanol metabolism of M. thermoacetica. Proteins 2007;67:167-176. V C 2007 Wiley-Liss, Inc.

Characterization of a Corrinoid Protein Involved in the C1 Metabolism of Strict Anaerobic Bacterium Moorella thermoacetica

Asymmetric synthesis of (1's,2'r)-cyclopropyl carbocyclic nucleosides

A corrinoid protein was induced and overexpressed in methanol-grown cells of the thermophilic anaerobic bacterium Moorella thermoacetica. The protein was purified from cytosolic extracts. After screening for crystallization conditions and optimization, crystals were obtained that diffracted strongly on a rotating-anode X-ray source. A diffraction data set was collected and processed including reflections to 1.9 A resolution. Reflections were indexed in a primitive orthorhombic cell with unit-cell parameters a = 55.69, b = 62.74, c = 34.54 A. N-­terminal amino-acid sequencing indicates that the crystals contain a C-­terminal fragment of the protein.

/pdf/isolation-crystallization-and-preliminary-x-ray-analysis-of-3k2g8l2zp9.pdf

Isolation, crystallization and preliminary X-ray analysis of a methanol-induced corrinoid protein from Moorella thermoacetica.

Synthesis of enantiomerically pure cyclopropyl carbocyclic nucleosides

From the hexane extract of the bark of Myrica cerifera, the pentacyclic triterpenes taraxerol and myricadiol were isolated. The EtOH extract afforded the [7.0]metacyclophanes, (±)-myricanol (4), and myricanone (7). Accurate 1 H- and 13 C-NMR spectral assignments have been made for (±)-myricanol (4), 5,11,17-tri-O-acetyl-(±)-myricanol (5), 11-O-methyl-(±)-myricanol (6), and myricanone (7) by a study of the 1 H- 1 H-COSY, 1 H- 13 C-COSY (HETCOR), selective INEPT, and 1D NOE experiments. The structure of (±)-myricanol was established by a single crystal X-ray analysis. Molecular mechanics MM-3(94) calculations have been made for (R,Sa)-and (S,Sa)-myricanol, and the bond lengths, bond angles, and the torsion angles have been calculated for the energy-minimized conformation

Doowon Lee

Papers

Characterization of a Corrinoid Protein Involved in the C1 Metabolism of Strict Anaerobic Bacterium Moorella thermoacetica

Asymmetric synthesis of (1's,2'r)-cyclopropyl carbocyclic nucleosides

Isolation, crystallization and preliminary X-ray analysis of a methanol-induced corrinoid protein from Moorella thermoacetica.

Synthesis of enantiomerically pure cyclopropyl carbocyclic nucleosides

Extensive 1D, 2D NMR Spectra of Some [7.0]Metacyclophanes and X-ray Analysis of (±)-Myricanol