Synthesis of Pyrrolidine- and γ-Lactam-Containing Natural Products and Related Compounds from Pyrrole Scaffolds

Polycyclic alkaloid natural products featuring pyrrolidine and pyrrolidinone motifs remain enduring targets of total synthesis endeavors. Pyrrole and its derivatives have been exploited to access many such frameworks, including alkaloids belonging to the Aspidosperma, Stemona, and batzelladine families. In this article, a selection of exemplars that highlight the utility of pyrrole-based approaches to facilitate total syntheses of pyrrolidine- and pyrrolidinone-containing alkaloids and related molecules are showcased.

Chemospecific Cyclizations of α-Carbonyl Sulfoxonium Ylides on Aryls and Heteroaryls

The functionalization of aryl and heteroaryls using α-carbonyl sulfoxonium ylides without the help of a directing group has remained so far a neglected area, despite the advantageous safety profile of sulfoxonium ylides. Described herein are the cyclizations of α-carbonyl sulfoxonium ylides onto benzenes, benzofurans and N-p-toluenesulfonyl indoles in the presence of a base in HFIP, whereas pyrroles and N-methyl indoles undergo cyclization in the presence of an iridium catalyst. Significantly, these two sets of conditions are chemospecific for each groups of substrates.

Methods for the synthesis of annulated pyrroles via cyclisation strategies

In this report, we review the methods that have been employed to synthesise annulated pyrroles.

Cyclic enaminones. Part II: applications as versatile intermediates in alkaloid synthesis

Among many other strategies, the enaminone approach is an important strategy to construct and diversify the azacyclic core in various alkaloids syntheses. In this brief review we discuss the application of cyclic enaminones as building blocks, as well as potential intermediates in the total synthesis of selected alkaloids.

4-Nitrophenyl 4-bromobenzoate

In the crystal structure of the title compound, C₁₃H₈BrNO₄, mol­ecules are linked into chains along [101] by weak C—H⋯O hydrogen bonds and Br⋯O contacts [3.140 (4) Å]. The planes of the nitrated and brominated aryl rings form a dihedral angle of 64.98 (10)°, indicating a twist in the mol­ecule.

Total syntheses of arylindolizidine alkaloids (+)-ipalbidine and (+)-antofine

This paper presents the first application of two recently developed reactions to natural product synthesis. The first method involves a 6-endo-trig cyclization to prepare a versatile chiral enaminone building block. The second is a direct C-H arylation reaction. As a showcase for the utility of these methods, (+)-antofine and (+)-ipalbidine were synthesized in only 8 steps and 24-26% overall yields.

Synthesis, in vitro and in vivo cytotoxicity of 6,7-diaryl-2,3,8,8a-tetrahydroindolizin-5(1H)-ones

A 6,7-diaryl-2,3,8,8a-tetrahydroindolizin-5(1H)-one library was constructed and tested against the colon cancer cell line HCT-116 as an initial screen for cytotoxic properties. Of this library, the parent compound, in which the southern aromatic ring remains unsubstituted, and the northern aromatic ring carries a 4-methoxy group, exhibited the most potent cytotoxicity with an IC50 value of 0.39 microM and displayed promising activity in vivo in the NCI's mouse hollow fiber assay.