The first total synthesis of 15-epi-annonin I

Developments in the Catalytic Asymmetric Synthesis of Agrochemicals and Their Synthetic Importance

Catalytic asymmetric synthesis has become an essential tool for the enantioselective synthesis of pharmaceuticals, natural products, and agrochemicals (mainly fungicides, herbicides, insecticides, and pheromones). With continuous growing interest in both modern agricultural chemistry and catalytic asymmetric synthesis chemistry, this review provides a comprehensive overview of some earlier reports as well as the recent successful applications of various catalytic asymmetric syntheses methodologies, such as enantioselective hydroformylation, enantioselective hydrogenation, asymmetric Sharpless epoxidation and dihydroxylation, asymmetric cyclopropanation or isomerization, organocatalyzed asymmetric synthesis, and so forth, which have been used as key steps in the preparation of chiral agrochemicals (on R&D, piloting, and commercial scales). Chiral agrochemicals can also lead the new generation of such chemicals having specific and novel modes of action for achieving sustainable crop protection and production. Some perspectives and challenges for these catalytic asymmetric methodologies in the synthesis of chiral agrochemicals are also briefly discussed in the final section of the manuscript. This review will provide the insight regarding understanding, development, and evaluation of catalytic asymmetric systems for the synthesis of chiral agrochemicals among the agrochemists.

Recent progress on the total synthesis of acetogenins from Annonaceae

An overview of recent progress on the total synthesis of acetogenins from Annonaceae during the past 12 years is provided. These include mono-tetrahydrofurans, adjacent bis-tetrahydrofurans, nonadjacent bis-tetrahydrofurans, tri-tetrahydrofurans, adjacent tetrahydrofuran-tetrahydropyrans, nonadjacent tetrahydrofuran-tetrahydropyrans, mono-tetrahydropyrans, and acetogenins containing only gamma-lactone. This review emphasizes only the first total synthesis of molecules of contemporary interest and syntheses that have helped to correct structures. In addition, some significant results on the novel synthesis and structure-activity relationship studies of annonaceous acetogenins are also introduced.

Stereocontrolled Synthesis of Key Advanced Intermediates toward Simplified Acetogenin Analogues

The stereo- and enantiocontrolled synthesis of substituted beta-hydroxy ethers based on glycol and catechol bearing an alkyne group and a series of substituents is reported. These substrates were designed to mimic the bis-THF array of annonaceous acetogenins and to provide an access to simplified and modified analogues. The key steps of the synthesis involve the condensation of the nonracemic mesylate of solketal with ethylene glycol and catechol, followed by an alkylation with a glycidyl derivative. Under appropriate conditions, the reaction is completely stereoselective and allows the synthesis of all the diastereomers. After the epoxide was opened with triethylsilylacetylene, the second epoxide was unmasked and reacted with a series of alkyl, aryl, amine, and alcohol reagents. A series of 28 analogues was prepared having a glycol or a catechol core, a stereodefined configuration of the flanking hydroxyl groups, and an acetylenic appendage suitable for a coupling to a lactone-bearing fragment.

Annonaceous acetogenins: recent progress

The Annonaceous acetogenins are promising new antitumor and pesticidal agents that are found only in the plant family Annonaceae. Chemically, they are derivatives of long-chain fatty acids. Biologically, they exhibit their potent bioactivities through depletion of ATP levels via inhibiting complex I of mitochondria and inhibiting the NADH oxidase of plasma membranes of tumor cells. Thus, they thwart ATP-driven resistance mechanisms. This review presents the progress made in the chemistry, biology, and development of these compounds since December 1995.