A practical and efficient route to the CD spiroketal (C-16-C-28) of the spongistatins is reported. Two stereocenters are introduced from chiral building blocks with the remainder introduced by substrate-controlled transformations. The key beta-keto-1,3-dithiane intermediate is generated by a dithiol conjugate addition to an ynone and the 1,3-dithiane unit in the C-ring plays a key role in the s...

After feeding of 24-ep/-castasterone to the cockroach Periplaneta americana an organspecific epimerization of the brassinosteroid to 2,24-d/ep/-castasterone could be detected in female insects. The metabolite being observed only in the ovaries and not in the testes of the insect was identified by GC/MS in comparison with a synthesized authentic sample. Con­ trary, 24-ep/-brassinolide is not met...

Different antibiotics have different characteristics but the aspect of antibiotic stability is the main concern of the pharmacist when dispensing the drug. The stability of drug such as chemical stability, physical stability, microbiological stability, therapeutic stability and toxicological stability will ensure its therapeutic effect. There are some factors that may affect antibiotics’ effect...

The Lattrell-Dax method of nitrite-mediated substitution of carbohydrate triflates is an efficient method to generate structures of inverse configuration. In this study it has been demonstrated that a neighboring equatorial ester group plays a highly important role in this carbohydrate epimerization reaction, inducing the formation of inversion compounds in good yields. Based on this effect, ef...

Photo-mediated 6π cyclization is a valuable method for the formation of fused heterocyclic systems. Here we demonstrate that irradiation of cyclic 2-aryloxyketones with blue LED light in the presence of an IrIII complex leads to efficient and high yielding arylation across a panoply of substrates by energy transfer. 2-Arylthioketones and 2-arylaminoketones also cyclize effectively under these c...

Rearranging hydrogen bonding groups adds nucleobases to an artificially expanded genetic information system (AEGIS), pairing orthogonally to standard nucleotides. We report here a large-scale synthesis of the AEGIS nucleotide carrying 2-amino-3-nitropyridin-6-one (trivially Z) via Heck coupling and a hydroboration/oxidation sequence. RiboZ is more stable against epimerization than its 2'-deoxyr...

Selected aldohexoses (D-glucose, D-mannose, and D-galactose) and aldopentoses (D-xylose, L-arabinose, and D-ribose) are readily available components of biopolymers. Isomerization reactions of these substances are very attractive as carbon-efficient processes to broaden the portfolio of abundant monosaccharides. This review focuses on the chemocatalytic isomerization of aldoses into the correspo...

The one-carbon bridge stereochemistry of bicyclo[3.3.1]nonane products formed in the Robinson annulation reactions of 2-substituted cyclohex-2-enones was investigated. In contrast to previous reports, it was found that the major diastereomer formed places the one-carbon bridge substituent anti to the beta-keto ester/amide unit introduced in the Robinson annulation. This stereoselectivity appear...

Matcha green tea powder (MGTP) is made with finely ground green tea leaves that are rich in phytochemicals, most particularly catechins. Shortbread biscuits were enriched with MGTP and evaluated for consumer acceptability and potential functional health properties. Baking decreased the content of total catechins by 19% compared to dough, although epimerization increased the amount of (+)-galloc...