Manganese dioxide mediated one-pot synthesis of methyl 9H-pyrido[3,4-b]indole-1-carboxylate: Concise synthesis of alangiobussinine

Silylacetate-promoted addition reaction of isocyanides to nitrones: effective synthesis of C(1)-carboxamide derivatives

We report an efficient method for the synthesis of C(1)-carboxamide derivatives by adding isocyanides to 3,4-dihydroisoquinoline N-oxides and 3,4-dihydro-β-carboline 2-oxide in the presence of TMSOAc. 3,4-Dihydroisoquinoline-1-carboxylamide derivatives and 9-dihydro-3H-pyrido[3,4-b]indole-1-carboxamide derivatives were obtained in reasonable yields. The method could be used to synthesize alangiobussine, an alkaloid, in 61% yield.

Cyclic Imines in Ugi and Ugi-Type Reactions

Ugi four-component reactions (U-4CRs) are widely recognized as being highly efficient for the synthesis of pseudopeptides. However, the products of these reactions are not so interesting as drug candidates because they are not conformationally restricted enough for a potent interaction with biological targets. One possible way to overcome this problem is to replace amine and oxo components in the U-4CRs with cyclic imines in so-called Joullié-Ugi three-component reactions (JU-3CRs). This approach provides a robust single-step route to peptide moieties connected to N-heterocyclic motifs that are found as core skeletons in many natural products and pharmaceutical compounds. JU-3CRs also provide much better diastereoselectivity than their four-component analogues. We survey here the redesign of many synthetic routes for the efficient preparation of a wide variety of three-, five-, six-, and seven-membered heterocyclic compounds connected to the peptide backbone. Additionally, in the Ugi reactions based on the cyclic imines, α-acidic isocyanides, or azides can be replaced with normal isocyanides or acids, respectively, leading to the synthesis of N-heterocycles attached to oxazoles or tetrazoles, which are of great pharmaceutical significance. This Review includes all research articles related to Ugi reactions based on the cyclic imines to the year 2020 and will be useful to chemists in designing novel synthetic routes for the synthesis of individual and combinatorial libraries of natural products and drug-like compounds.

Natural carbolines inspired the discovery of chiral CarOx ligands for asymmetric synthesis and antifungal leads

Natural carboline-inspired novel chiral β-CarOx ligands were designed and synthesized for asymmetric synthesis and discovery of antifungal leads.

IBX-mediated oxidative addition of isocyanides to cyclic secondary amines: total syntheses of alangiobussine and alangiobussinine

The present study describes a robust and general method for the synthesis of C(1)-carboxamides through IBX-mediated oxidative addition of isocyanides to tryptolines and 1,2,3,4-tetrahydroisoquinolines. In this transformation, IBX plays a dual role of an oxidant and Lewis acid to activate imine facilitating isocyanide addition. Detailed mechanistic investigations were performed by isotopic labeling and real-time NMR experiments. The method was utilized for the gram scale syntheses of two alkaloids alangiobussine and alangiobussinine in 63% and 45% overall yield, respectively.

In vitro inhibitory and cytotoxic activity of MFM 501, a novel codonopsinine derivative, against Methicillin-Resistant Staphylococcus aureus clinical isolates

28 new pyrrolidine types of compounds as analogues for natural polyhydroxy alkaloids of codonopsinine were evaluated for their anti-MRSA activity using MIC and MBC value determination assay against a panel of S. aureus isolates. One pyrrolidine compound, MFM 501, exhibited good inhibitory activity with MIC value of 15.6 to 31.3 μg/mL against 55 S. aureus isolates (43 MRSA and 12 MSSA isolates). The active compound also displayed MBC values between 250 and 500 μg/mL against 58 S. aureus isolates (45 MRSA and 13 MSSA isolates) implying that MFM 501 has a bacteriostatic rather than bactericidal effect against both MRSA and MSSA isolates. In addition, MFM 501 showed no apparent cytotoxicity activity towards three normal cell lines (WRL-68, Vero, and 3T3) with IC₅₀ values of >625 µg/mL. Selectivity index (SI) of MFM 501 gave a value of >10 suggesting that MFM 501 is significant and suitable for further in vivo investigations. These results suggested that synthetically derived intermediate compounds based on natural products may play an important role in the discovery of new anti-infective agents against MRSA.