Lanthanide complexes as luminogenic probes to measure sulfide levels in industrial samples

A series of lanthanide-based, azide-appended complexes were investigated as hydrogen sulfide-sensitive probes. Europium complex 1 and Tb complex 3 both displayed a sulfide-dependent increase in luminescence, while Tb complex 2 displayed a decrease in luminescence upon exposure to NaHS. The utility of the complexes for monitoring sulfide levels in industrial oil and water samples was investigated. Complex 3 provided a sensitive measure of sulfide levels in petrochemical water samples (detection limit ∼ 250 nM), while complex 1 was capable of monitoring μM levels of sulfide in partially refined crude oil.     

A Divergent Enantioselective Strategy for the Synthesis of Griseusins

The first enantioselective total synthesis of griseusin A, griseusin C, 4′‐deacetyl‐griseusin A, and two non‐native counterparts in 11–14 steps is reported. This strategy highlights a key hydroxy‐directed C? H olefination of 1‐methylene isochroman with an α,β‐unsaturated ketone followed by subsequent stereoselective epoxidation and regioselective cyclization to afford the signature tetrahydro‐spiropyran ring. Colorectal cancer cell cytotoxicities of the final products highlight the impact of the griseusin tetrahydro‐spiropyran ring on bioactivity. As the first divergent enantioselective synthesis, the strategy put forth sets the stage for further griseusin mechanism‐of‐action and SAR studies.     

Incorporation of glucose analogs by GtfE and GtfD from the vancomycin biosynthetic pathway to generate variant glycopeptides

Analogs of the glycopeptide antibiotics vancomycin and teicoplanin with alterations in one or both sugar moieties of the disaccharide have been prepared by tandem action of the vancomycin pathway glycosyltransferases GtfE and GtfD. All four regioisomers (2-, 3-, 4-, 6-) of TDP-deoxyglucoses and UDP/TDP-aminoglucoses were prepared, predominantly by action of D-glucopyranosyl-1-phosphate thymidylyltransferase, E(p). GtfE transferred the deoxyglucoses or aminoglucoses onto the 4-OH of 4-hydroxyphenylglycine of both the vancomycin and teicoplanin aglycone scaffolds. Kinetic analysis indicated the 2-, 3-, 4-, and 6-amino-glucoses were transferred by GtfE with only a 4- to 30-fold drop in k(cat) and no effect on K(m) compared to the native substrate, UDP/TDP-glucose, suggesting preparative utility. The next enzyme, GtfD, could utilize the variant glucosyl-peptides as substrates for transfer of L-4-epi-vancosamine. The aminosugar moieties in these variant glycopeptides introduce sites for acylation or reductive alkylation.