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

Applications of NMR Spectroscopy in Organic Chemistry.

1. Introdution A 2. Early Developments B 2.1. First Reports B 2.2. Heterocycle Synthesis E 2.3. Nitroalkene Synthesis G 2.4. Synthesis of Dinitroamines G 2.5. Reactions with Preformed Imines H 2.6. Conjugate Addition Nitro-Mannich Reactions H 2.7. Reactions of Nitroesters I 3. Noncatayltic Reactions J 3.1. Base-Mediated Reactions J 3.2. Reactions of α-Amido Sulfones K 3.3. Auxiliary Controlled Stereoselective Reactions L 3.4. Reformatsky-Type Reactions M 3.5. Electrochemically Induced Nitro-Mannich Reactions N 4. Indirect Metal-Catalyzed Reactions N 4.1. Racemic Reactions N 4.2. Asymmetric Reactions N 5. Direct Metal-Catalyzed Reactions O 5.1. Racemic Reactions O 5.2. Asymmetric Reactions P 6. Organocatalytic Reactions T 6.1. Racemic Reactions T 6.2. Asymmetric Reactions U 6.2.1. Urea/Thiourea Catalysts U 6.2.2. Brønsted Acid Catalysts X 6.2.3. Phase-Transfer Catalysts Y 6.2.4. Brønsted-Base Catalysts Z 7. Reactions of Ketimines AA 7.1. Racemic Reactions AA 7.2. Auxiliary Controlled Reactions AB 7.3. Catalytic Enantioselective Reactions AB 8. Reactions of α-Nitroesters AC 9. Reactions of α-Nitrophosphonates AE 10. Conjugate Addition Nitro-Mannich Reactions AF 10.1. Organocatalytic Reactions of Carbon Nucleophiles AF 10.2. Reactions with Organometallic Nucleophiles AG 10.3. Aza-Morita−Baylis−Hillman Reactions AI 10.4. Synthesis of 3-Nitrochromene Derivatives AI 10.5. [3 + 2] Cycloadditions AJ 10.6. [2 + 2] Cycloadditions AL 11. Cascade Reactions AL 11.1. Nitro-Mannich/Lactamization Cascades AL 11.2. Other Cascade Reactions AO 12. Cross-Dehydrogenative Coupling Reactions AP 13. Miscellaneous Reactions AQ 13.1. Reactions of Isoquinolines AQ 13.2. Reactions of Trinitromethane AR 14. Applications to Synthesis AR 14.1. Peptide Synthesis AU 15. Summary AU Author Information AW Corresponding Author AW Notes AW Biographies AW Acknowledgments AX References AX

Nitro-Mannich reaction.

Nucleophilic dearomatizing (DNAr) reactions of aromatic C,H-systems. A mature paradigm in organic synthesis.

Synthesis, biology and clinical significance of pentacyclic triterpenes: a multi-target approach to prevention and treatment of metabolic and vascular diseases

Glycyrrhizic acid derivatives as influenza A/H1N1 virus inhibitors.

Glycyrrhizic acid derivatives as Dengue virus inhibitors

N-(methylcytisinyl)-N′-substituted ureas, N-substituted cytisine-12-carbamides, and cytisine-12-thiocarbamide were prepared by reaction of (–)-cytisine with urea and thiourea and of (–)-cytisine and its 12-N-methyl-3-amino derivative with isocyanates. Their specific nootropic activity was studied in vivo. The therapeutic index was determined for the lead compound. Promising candidates for further pharmacological testing were found.

Synthesis and specific nootropic activity of (-)-cytisine derivatives with carbamide and thiocarbamide moieties in their structure

Oxidation of betulin by pyridinium dichromate, pyridinium chlorochromate, and K2Cr2O7 -H2SO4 in the presence of tetrabutylammonium bromide was studied. Products of regioselective C-3, C-28-, and exhaustive oxidation, 28-hydroxylup-20(29)-3-one, 3β-hydroxy- and 3-oxolup-20(29)-en-28-al were obtained.

Selective Oxidation of Betulin by Cr(VI) Reagents

Diterpenoid alkaloids comprise a large group of natural compounds produced by the plants of the genera Aconitum and Delphinium. Some of these compounds were found to manifest valuable pharmacological properties, including the unique antiarrhythmic activity. Allapinine (derived from the alkaloid lappaconitine) was approved as a drug. The investigation of the structure—activity relationship revealed structural elements responsible for the arrhythmogenic and antiarrhythmic properties.

M. S. Yunusov

Papers

Glycyrrhizic acid derivatives as influenza A/H1N1 virus inhibitors.

Glycyrrhizic acid derivatives as Dengue virus inhibitors

Synthesis and specific nootropic activity of (-)-cytisine derivatives with carbamide and thiocarbamide moieties in their structure

Selective Oxidation of Betulin by Cr(VI) Reagents

Antiarrhythmic agents based on diterpenoid alkaloids