Stereoselective synthesis of (−)-microcarpalide

A highly convergent and efficient synthesis of (−)-microcarpalide, a 10-membered lactone displaying remarkable microfilament disrupting activity is described. Ring-closing metathesis and Sharpless asymmetric dihydroxylations are the key steps. Our strategy highlights the application of novel hydroxy lactone precursors for the stereoselective synthesis of (−)-microcarpalide.     

Asymmetric synthesis of heteroorganic analogs of natural products. 6. (S)-α-amino-ω-phosphonocarboxylic acids

Alkylation, by -haloalkylphosphonates, of the Ni(II) complex of the Schiff base formed from glycine and (S)-2-N-(N¹-benzylprolyl)-o-aminobenzophenone has been used for the asymmetric synthesis of (S)-2-amino-4-phosphonobutyric and (S)-2-amino-5-phosphonovaleric acids.Institute of Bioorganic Chemistry and Oil Chemistry, Ukrainian Academy of Sciences, 250800 Kiev. A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 397–402, February, 1992.     

A Novel Asymmetric Synthesis of （-）-cis-1, 3-Dibenzylhexahydrofuro[3, 4-d]imidazole-2,4-dione

(-)-cis-1, 3-Dibenzyl-hexahydrofuro[3, 4-d]imidazole-2, 4-dione was prepared by a new synthesis method from meso dicarboxylic acid and dehydroabietylamine by asymmetric reduction in good yield with up to 91.6% e.e. value.     

In the golden age of organocatalysis

The term "organocatalysis" describes the acceleration of chemical reactions through the addition of a substoichiometric quantity of an organic compound. The interest in this field has increased spectacularly in the last few years as result of both the novelty of the concept and, more importantly, the fact that the efficiency and selectivity of many organocatalytic reactions meet the standards of established organic reactions. Organocatalytic reactions are becoming powerful tools in the construction of complex molecular skeletons. The diverse examples show that in recent years organocatalysis has developed within organic chemistry into its own subdiscipline, whose "Golden Age" has already dawned.     

Amino acid catalyzed neogenesis of carbohydrates: a plausible ancient transformation

Hexose sugars play a fundamental role in vital biochemical processes and their biosynthesis is achieved through enzyme-catalyzed pathways. Herein we disclose the ability of amino acids to catalyze the asymmetric neogenesis of carbohydrates by sequential cross-aldol reactions. The amino acids mediate the asymmetric de novo synthesis of natural L- and D-hexoses and their analogues with excellent stereoselectivity in organic solvents. In some cases, the four new stereocenters are assembled with almost absolute stereocontrol. The unique feature of these results is that, when an amino acid is employed as the catalyst, a single reaction sequence can convert a protected glycol aldehyde into a hexose in one step. For example, proline and its derivatives catalyze the asymmetric neogenesis of allose with >99 % ee in one chemical manipulation. Furthermore, all amino acids tested catalyzed the asymmetric formation of natural sugars under prebiotic conditions, with alanine being the smallest catalyst. The inherent simplicity of this catalytic process suggests that a catalytic prebiotic "gluconeogenesis" may occur, in which amino acids transfer their stereochemical information to sugars. In addition, the amino acid catalyzed stereoselective sequential cross-aldol reactions were performed as a two-step procedure with different aldehydes as acceptors and nucleophiles. The employment of two different amino acids as catalysts for the iterative direct aldol reactions enabled the asymmetric synthesis of deoxysugars with >99 % ee. In addition, the direct amino acid catalyzed C(2)+C(2)+C(2) methodology is a new entry for the short, highly enantioselective de novo synthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric de novo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic asymmetric transformation (DYKAT) mediated by an amino acid.     

Enantioselective Oxidation of Sulfides Catalyzed by Chiral MoV and CuII Complexes of Catechol-Appended β-Cyclodextrin Derivatives in Water

The two modified β-cyclodextrin (β-CD) derivatives having catechol-type ligand (2,3- and 3,4-dihydroxy groups on the benzoate ring) were synthesized. The chiral catalytic activity of their Mo^V and Cu^II complexes was examined in the asymmetric oxidation of aromatic sulfides using hydrogen peroxide in water (pH 6.0). The oxidation with the Mo^V complexes of two β-CD derivatives were more accelerated than that with the Cu^II complexes. The sign of the optical rotation of the sulfoxides obtained in the above two cases showed the opposite configuration in the oxidation of the same sulfide. The difference of the enantioselectivity appeared also between the two complexes of the 2,3- and 3,4-dihydroxybenzoate derivatives with the same metal ion. While the use of the Mo^V complexes with the catechol derivatives yielded the sulfoxides with 35–65% ee, the use of the Cu^II complexes gave the products with the␣opposite configuration at 26–52% ee. The chiral induction in the oxidation, observed conversely between the␣catalysts, was reflected on the chiral conformation of the respective metal catalysts, showed in Induced Circular Dichroism (ICD) spectra. The highest optical yield, 65%, was observed in the oxidation of butyl phenyl sulfide using the catalytic amount (0.1 equiv) of the Mo^V complex with mono-6-O-(3,4-dihydroxybenzoyl)-β-CD. The reaction gave predominantly the (S)-sulfoxide in 95% chemical yield.     

Asymmetric multicomponent reactions (AMCRs): the new frontier

Asymmetric multicomponent reactions involve the preparation of chiral compounds by the reaction of three or more reagents added simultaneously. This kind of addition and reaction has some advantages over classic divergent reaction strategies, such as lower costs, time, and energy, as well as environmentally friendlier aspects. All these advantages, together with the high level of stereoselectivity attained in some of these reactions, will force chemists in industry as in academia to adopt this new strategy of synthesis, or at least to consider it as a viable option. The positive aspects as well as the drawbacks of this strategy are discussed in this Review.     

Stereocontrol in Organic Synthesis Using the Diphenylphosphoryl Group

In 1959, Horner showed that metalated alkyldiphenylphosphane oxides react with aldehydes or ketones to give alkenes. With this reaction, the diphenylphosphoryl (Ph₂PO) group made its entrance into synthetic organic chemistry. In the thirty-six years since that date, extensive research has shown that this olefination, the Horner–Wittig reaction, has unique properties that make it much more than simply the phosphane oxide cousin of the more famous phosphorus-based olefinations—the Wittig reaction (based on phosphonium salts) and the Wadsworth–Emmons reaction (based on phosphonate esters). Early work on the Horner–Wittig reaction concentrated on the reactivity of phosphane oxides and the regioselectivity of their reactions, but more recently the power of the Ph₂PO group to control the stereochemistry of alkenes, and to produce “on demand” either stereoisomer in high stereochemical purity, has emerged. From the study of these stereocontrolled Horner–Wittig reactions arose the realization that the Ph₂PO group is useful not only for the control of the two-dimensional stereochemistry of alkenes, but also of three-dimensional stereochemistry in general. After a brief introduction to phosphane oxide chemistry, this review will examine the Horner–Wittig reaction, in both its original and “stereocontrolled” varieties. From there, we will move on to an account of the stereoselective construction of molecules containing the Ph₂PO group, concentrating on the stereochemical directing effects of the Ph₂PO group and on the role of its unique combination of attributes—steric bulk, electronegativity, and Lewis basicity—in controlling these reactions. Finally, we will present what is intended as a practical guide to this chemistry, covering the type of functionalized alkenes that have been made with the help of the Ph₂PO group and giving guidelines that we hope will help the organic chemist to make the most of the chemistry the Ph₂PO group has to offer.     

烯丙基二异雪松基硼烷的制备及其与羰基化合物的不对称反应

本文以(-)-α-雪松烯为原料, 制备了烯丙基二异雪松基硼烷(Icd~2B-CH~2CH=CH~2). 该手性硼烷很容易与醛反应生成相应的烯丙基取代的手性仲醇, 光学产率在60%e.e.左右. 与潜手性酮反应的光学产率低于30%e.e..     

A Versatile Approach for the Asymmetric Synthesis of 3-Alkyl-isoindolin-1-ones

3 Ｓｕｂｓｔｉｔｕｔｅｄｉｓｏｉｎｄｏｌｉｎ 1 ｏｎｅｓ (2 ,3 ｄｉｈｙｄｒｏ 1Ｈ ｉｓｏｉｎｄｏｌｉｎ 1 ｏｎｅｓ)ｏｆｇｅｎｅｒａｌｓｔｒｕｃｔｕｒｅ (1)ｃｏｎｓｔｉｔｕｔｅｔｈｅｋｅｙｓｔｒｕｃｔｕｒａｌｆｅａｔｕｒｅｏｆａｌａｒｇｅｎｕｍｂｅｒｏｆｂｉｏａｃｔｉｖｅｍｏｌｅｃｕｌｅｓｏｆｎａｔｕｒａｌｏｒｓｙｎｔｈｅｔｉｃｏｒｉｇｉｎ .Ｆｏｒｅｘａｍｐｌｅ ,ｌｅｎｎｏｘａｍｉｎｅ (2 ) ,1ｎｕｅｖａｍｉｎｅａｎｄｃｈｉｌｅｎｉｎｅａｒｅａｌｋａｌｏｉｄｓｉｓｏｌａｔｅｄｆｒｏｍｖａｒｉｏｕｓ…