Hannah Baars

N-Cyano Sulfoximines: COX Inhibition, Anticancer Activity, Cellular Toxicity, and Mutagenicity

From insects to cancer: N-Cyano sulfoximines were evaluated for COX inhibition and antiproliferative activity against a panel of cancer cell lines. The most active compound exhibited potent COX-2 inhibition, some selectivity for COX-2 over COX-1, only slight cytotoxicity towards healthy cells (HaCaT skin cells), and no mutagenic potential (as determined by an Ames assay).

Transition-Metal-Free Synthesis of Benzimidazoles Mediated by KOH/DMSO

Benzimidazoles are prepared by intramolecular N-arylations of amidines mediated by potassium hydroxide in DMSO at 120 °C. In this manner, diversely substituted products have been obtained in moderate to very good yields.

Metal-Catalyzed Syntheses of Abridged CDE Rings of Rubriflordilactones A and B

The development of complementary palladium- and cobalt-catalyzed approaches to tricyclic arylsilanes suitable for elaboration into the CDE ring systems of rubriflordilactones A and B is reported. Microwave conditions are required to effect a cobalt-catalyzed triyne cyclotrimerization, which critically depends on the substitution pattern of the triyne termini. Mild conditions to elaborate these arylsilanes to the CDE cores of the natural products are described.

Total Synthesis of (+)‐Rubriflordilactone A

Two enantioselective total syntheses of the nortriterpenoid natural product rubriflordilactone A are described, which use palladium- or cobalt-catalyzed cyclizations to form the CDE rings, and converge on a late-stage synthetic intermediate. These key processes are set up through the convergent coupling of a common diyne component with appropriate AB-ring aldehydes, a strategy that sets the stage for the synthetic exploration of other members of this family of natural products.

Enantioselective Synthesis of the Predominant AB Ring System of the Schisandra Nortriterpenoid Natural Products

An enantioselective synthesis of the AB ring system common to the majority of the Schisandra nortriterpenoid natural products is reported. Key steps include a stereospecific ring opening of a trisubstituted epoxide and the use of a β-lactone to enable installation of the gem-dimethyl functionality of the B ring. An acetalization strategy played a key role in a late-stage biomimetic AB ring bicyclization.

Synthesis of Alfaprostol and PGF2α through 1,4-Addition of an Alkyne to an Enal Intermediate as the Key Step

The veterinary drug Alfaprostol and prostaglandin PGF2α have been synthesized in just nine steps. The strategy involved the conjugate addition of an alkyne to a bicyclic enal, available in three steps by a proline-catalyzed aldol reaction of succinaldehyde. In the case of Alfaprostol, this resulted in the shortest synthesis reported to date. For PGF2α, this approach improved our previous route by making the 1,4-addition and ozonolysis more operationally simple.

Total Synthesis of the Schisandraceae Nortriterpenoid Rubriflordilactone A

Abstract Full details of the total synthesis of the Schisandraceae nortriterpenoid natural product rubriflordilactone A are reported. Palladium‐ and cobalt‐catalyzed polycyclizations were employed as key strategies to construct the central pentasubstituted arene from bromoendiyne and triyne precursors. This required the independent assembly of two AB ring aldehydes for combination with a common diyne component. A number of model systems were explored to investigate these two methodologies, and also to establish routes for the installation of the challenging benzopyran and butenolide rings.