Despite significant progress in the development of site-selective aliphatic C–H oxidations over the past decade, the ability to oxidize strong methylene C–H bonds in the presence of more oxidatively labile aromatic functionalities remains a major unsolved problem. Such chemoselective reactivity is highly desirable for enabling late stage oxidative derivatizations of pharmaceuticals and medicinally important natural products that often contain such functionality. Herein we report a simple manganese small molecule catalyst Mn(CF 3 –PDP) system that achieves such chemoselectivity via an unexpected synergy of catalyst design and acid additive. Preparative remote methylene oxidation is obtained in 50 aromatic compounds housing medicinally relevant halogen, oxygen, heterocyclic, and biaryl moieties. Late stage methylene oxidation is demonstrated on four drug scaffolds, including the ethinylestradiol scaffold where other non-directed C–H oxidants that tolerate aromatic groups effect oxidation at only activated tertiary benzylic sites. Rapid generation of a known metabolite (piragliatin) from an advanced intermediate is demonstrated.

Amide-containing molecules are ubiquitous in natural products, pharmaceuticals, and materials science. Due to their intermediate electron-richness, they are not amenable to any of the previously developed N-protection strategies known to enable remote aliphatic C—H oxidations. Using information gleaned from a systematic study of the main features that makes remote oxidations of amides in peptide settings possible, we developed an imidate salt protecting strategy that employs methyl trifluoromethanesulfonate (MeOTf) as a reversible alkylating agent. The imidate salt strategy enables, for the first time, remote, non-directed, site-selective C(sp3)—H oxidation with Fe(PDP) and Fe(CF3PDP) catalysis in the presence of a broad scope of tertiary amides, anilide, 2-pyridone, and carbamate functionality. Secondary and primary amides can be masked as N-Ns amides to undergo remote oxidation. This novel imidate strategy facilitates late-stage oxidations in a broader scope of medicinally important molecules and may find use in other C—H oxidations and metal-mediated reactions that do not tolerate amide functionality.

The first total synthesis of (-)-marinisporolide C is described, which establishes unequivocally the relative and absolute configuration of this oxopolyene macrolide. Key features of this synthesis include a series of highly stereoselective aldol reactions followed by directed reductions to build the polyol domain, a Stille cross-coupling reaction to assemble the polyene, and an intramolecular Horner-Wadsworth-Emmons olefination to forge the macrocyclic ring. Despite the initial approach to marinisporolide A using a Yamaguchi macrolactonization reaction that was unsuccessful due to steric hindrance of the oxygen at the C33 position, we were able to prepare a known derivative of marinisporolide A and consequently confirm its stereochemical assignment.

A stereoselective total synthesis of (-)-cryptocaryol A (1) is described. Key features of the 17-step route include the use of three boron-mediated aldol reaction-reduction sequences to control all stereocenters and an Ando modification of the Horner-Wadsworth-Emmons olefination that permitted the installation of the Z double bond of the α-pyrone ring.

Piperlongumine is a natural amide alkaloid isolated from several species of Piper and is described in the literature as selectively cytotoxic to several cancer cell lines. Inhibiting cell migration has gained considerable interest as an approach for discovering antimetastatic agents because this process is fundamental to metastasis. Piperlongumine, selected from cell-based assay screening of NuBBE Database, inhibited the migration of MDA-MB-231 breast cancer cells with an EC 50 of 3.0 ± 1.0 µM by the Boyden chamber assay. A series of five analogous compounds based on the structure of piperlongumine were designed, synthesized and evaluated in cell migration and cytotoxicity assays. The analogue designed by molecular simplification ((E)-N-acryloyl-3-(3,4,5-trimethoxyphenyl)acrylamide) was the most active of the series, with an EC 50 of 1.5 ± 1 µM. Additionally, this compound was selectively cytotoxic, with a selectivity index (SI) of 4.4. Keywords: piperlongumine, piplartine, piperamide, cytotoxicity, cell migration inhibition IntroductionMetastasis is the process by which undifferentiated cancer cells migrate to other parts of the body.1,2 Suppression of metastasis is an urgent need in cancer treatment, as most existing drugs only inhibit cell proliferation.3 Traditionally, chemotherapy is based on cytotoxic therapeutic agents that inhibit proliferation and cause cell death. However, the strategy of inhibiting cell migration has recently gained considerable interest. 4 Several compounds that inhibit the process of metastasis have been described to date. 5,6 Paclitaxel, which was originally discovered as an antimitotic agent that disrupts the cell cycle in cancer cells by stabilizing microtubules, exhibits marked and selective inhibition of tumor cell migration. 7As extensively reviewed elsewhere, biodiversity in nature has provided unique chemical scaffolds that have been used as templates for medicinal chemistry and drug discovery. [8][9][10][11][12][13] The availability of natural compound libraries is of significant importance for integrating natural products and medicinal chemistry, especially for the identification of new bioactive agents and the rational design of compounds in drug discovery.14 Within this context, we selected the natural product piperlongumine (1), also known as piplartine, from cell-based assay screening of NuBBE Database (NuBBE DB ) 15 and evaluated its ability to inhibit Synthetic Analogue of the Natural Product Piperlongumine as a Potent Inhibitor of Breast Cancer Cell Line Migration J. Braz. Chem. Soc. 476 cancer cell migration using biological and target-based experiments.Piperlongumine (1, Figure 1) is an alkamide isolated from several species of Piper (Piperaceae). 16 It is described as possessing antifungal properties, 17 cytotoxicity toward several cancer cell lines, 18,19 and trypanocidal effects, 20 as well as other biological activities. 21 Furthermore, piperlongumine selectively induces cell death in cancer cells but does not reduce viability in normal cells. 22This ...

In this communication, the enantioselective synthesis of phthalides and isochromanones is described through a new palladium‐catalyzed Heck–Matsuda arylation/NaBH4‐reduction/lactonization sequence of 2,3‐ and 2,5‐dihydrofurans in good overall yields and excellent enantioselectivities (up to 98:2 er). This expeditious synthesis of chiral Heck lactol intermediates allowed the diversification of the strategy to obtain medicinally relevant chiral lactones, amines, and olefins. The natural product 3‐butylphthalide was obtained in three steps with an overall yield of 33 % yield in 98:2 er.

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The selectivity of aldol reactions involving kinetic enolates is related to various factors such as the nature of the Lewis acid (Li, Mg, B, Al, Ti, Sn, etc.), the presence of stereogenic centers in both the substrates and reagents, the nature of their substituents and the reaction conditions. Another factor of major importance is the nature of the enolate double bond (Z or E) [1].In general, it is well known that in aldol reactions involving metal enolates, which proceed through a six-membered cyclic transition state, the Z-enolate leads to the formation of 1,2-syn aldol adducts and the E-enolate affords aldol adducts with the 1,2-anti configuration. A rationalization for the observed selectivities of these aldol reactions was proposed by Zimmerman and Traxler (Scheme 5.1) [2]. According to this model, the nature of the double bond geometry plays a primary role in determining the energies of the competing transition states. For Z-enolates, the transition state TS2 is more destabilized than transition state TS1 because of the 1,3-diaxial interactions between the R 1 and R 3 substituents as well as between these substituents and one of the metal ligands (L). Therefore, the Z-enolate preferentially leads to the formation of the 1,2-syn aldol adduct.For the E-enolate, 1,3-diaxial interactions between the R 1 and R 3 substituents and between both R 1 and R 3 and one of the metal ligands are present in transition state TS4. Therefore, the 1,2-anti aldol adduct is obtained from the lower energy transition state TS3.Modern aldol reactions use preformed enolates to obtain good yields by preventing side reactions. This methodology has proven to be very effective for various Lewis acids derived from lithium, titanium, tin, and boron. By using preformed enolates with chiral substrates and reagents, it is possible to obtain aldol adducts with an excellent degree of asymmetric induction.The IUPAC defines asymmetric induction as the traditional term describing the preferential formation in a chemical reaction of one enantiomer (or diastereomer) over the other as a result of a chiral feature present in the substrate, reagent, catalyst, or the environment [3].