Copper-catalyzed deacetonative Sonogashira coupling

A convenient Pd- and phosphine-free protocol for assembling internal alkynes from tertiary propargyl alcohols and (het)aryl halides has been developed. The proposed tandem approach includes the base-promoted retro-Favorskii fragmentation followed by Cu-catalyzed C(sp)-C(sp²) cross-coupling. The use of inexpensive reagents (e.g. a catalyst, additives, a base, and a solvent) and good functional group tolerance make the procedure practical and cost-effective. The synthetic utility of the method was demonstrated by a smooth alkynylation of vinyl iodides derived from natural steroidal hormones.

Highly Enantioselective Synthesis of Functionalized Glutarimide Using Oxidative N-Heterocyclic Carbene Catalysis: A Formal Synthesis of (-)-Paroxetine

A simple yet highly effective approach toward enantioselective synthesis of trans-3,4-disubstituted glutarimides from readily available starting materials is developed using oxidative N-heterocyclic carbene catalysis. The catalytic reaction involves a formal [3 + 3] annulation between enals and substituted malonamides enabling the production of glutarimide derivatives in a single chemical operation via concomitant formation of C-C and C-N bonds. The reaction offers easy access to a broad range of functionalized glutarimides with excellent enantioselectivity and good yield. Synthetic application of the method is demonstrated via formal synthesis of (-)-paroxetine and other bioactive molecules.

Synthesis and Biological Evaluation of Lactimidomycin and Its Analogues

The studies culminating in the total synthesis of the glutarimide-containing eukaryote translation elongation inhibitor lactimidomycin are described. The optimized synthetic route features a Zn(II)-mediated intramolecular Horner-Wadsworth-Emmons (HWE) reaction resulting in a highly stereoselective formation of the strained 12-membered macrolactone of lactimidomycin on a 423 mg scale. The presence of the E,Z-diene functionality was found to be key for effective macrocyclizations as a complete removal of these unsaturation units resulted in exclusive formation of the dimer rather than monocyclic enoate. The synthetic route features a late-stage installation of the glutarimide functionality via an asymmetric catalytic Mukaiyama aldol reaction, which allows for a quick generation of lactimidomycin homolog 55 containing two additional carbons in the glutarimide side chain. Similar to lactimidomycin, this analog was found to possess cytotoxicity against MDA-MB-231 breast cancer cells (GI50 =1-3 μM) using in vitro 2D and 3D assays. Although lactimidomycin was found to be the most potent compound in terms of anticancer activity, 55 as well as truncated analogues 50-52 lacking the glutarimide side-chain were found to be significantly less toxic against human mammary epithelial cells.