Current Organic Chemistry - Volume 22, Issue 2, 2018

The aim of this review is to provide a detailed account of the total synthetic approaches toward glycosylated Macrolide A. Mandelaide A was isolated from Lissoclinum Ascidian species found in Algoa Bay, South Africa and has been reported to exhibit potent cytotoxicity against a human lung cancer and a mouse neuroblastoma cell line. We have summarized the maneuvers in each paper by graphically detailing the synthesis, and associated reaction niceties, of only the key intermediates prepared by each research group. Fascinating structural feature of mandelalide A is a 24-membered α,β-unsaturated macrolactone, which contains a conjugated diene, a trisubstituted tetrahydrofuran (THF) segment, and a trisubstituted tetrahydropyran (THP) moiety attached to an unusual carbohydrate unit, 2-O-methyl-α-L-rhamnose. The macrolide is decorated with twelve challenging stereocenters being the part of oxygen containing heterocyclic rings. The total synthesis of mandelalide A involves a variety of renowned reactions which include Prins cyclization for the diastereoselective construction of tetrahydropyran subunit, Rychnovsky-Bartlett cyclization for the diastereoselective construction of tetrahydrofuran moiety, construction of the tetrahydropyran segment, Suzuki coupling, Horner-Wadsworth-Emmons (HWE) macrocyclization, Shiina-type macrolactonization, Sonogashira cross-coupling, Silver catalyzed cyclizations, alkyne metathesis and glycosylation to append the L-rhamnose-derived pyranoside. This review provides a critical account along with a comparison of the synthetic efforts directed to this important natural product and its analogues.

Background: 2,2-Disubstituted-1,3-dicarbonyls, including iodonium ylides, indanedioneketene precursors, sulfur ylides, 2,2-difluoro-1,3-diketones, 2,2-dihydroxyl- 1,3-diketones and cyclopropyl 1,3-dicarbonyls, are important intermediates in organic synthesis. Methodology: They are used in the preparation of various amides, benzofurans, furanones, quinones, and so on. However, there is no review to summarize their multiperformance and fundamental mechanisms. Conclusion: This review will focus on recent applications of 2,2-disubstituted-1,3- dicarbonyls mainly based on three reactivity patterns, which may enlighten the further research.

Background: Alkaloids are a diverse group of naturally occurring secondary metabolites which exhibit various pharmacological properties. They have been synthesized via various synthetic routes in order to study their medicinal efficacy and structure activity relationships. Methodology: Keeping in view the pharmaceutical significance of this class of compounds, the present review has been written with a focus on the synthetic approaches used for efficient construction of isoquinoline scaffolds in natural alkaloids including crispine A, emetine, erythrocarine, jamatine, annosqualine, morphine, lemonomycin, papaverine, berberine, and codeine. Conclusion: The main goal behind the compilation of these schemes is to inspire organic chemists and help reinvigorate the development of novel strategies for the synthesis of isoquinoline alkaloids and their derivatives in the future.

Background: The reaction of aryl halides or vinyl halides with activated alkenes in the presence of Palladium-catalyst along with a base for the formation of the C-C bond is called the Heck reaction. This reaction has been employed extensively in the synthesis of heterocyclic compounds. Methodology: We have highlighted these applications in 2010. Conclusion: This review aims to cover the recent application of the Heck reaction in the synthesis of heterocyclic compounds during a period from 2010 to 2017.

β-lactams have attracted a significant attention due to their potential biological activities and wide variety of synthetic applications. Developing novel and efficient methods for construction of functionalized β-lactams has been the subject of a number of papers in recent years. N-Propargyl amines/amides are one of the most specific class of alkynes having diverse reaction patterns. It is well known that they can undergo a number of cyclization reactions to produce various significant nitrogen containing heterocycles. This review surveys literature methods for the synthesis of highly substituted β-lactams from simple and easily available N-propargyl amine/amide derivatives from 1991 to 2017.