An efficient electrophilic alkynylation of azlactones (oxazol-5(4H)-ones) is developed using alkynyl(phenyl)iodonium salts as the electrophilic alkyne source. After remarkably short reaction times, the desired alkyne functionalized azlactones are obtained in 60-97% yield and can be transformed easily into a variety of quaternary α-amino acid derivatives.
On the way towards a new total synthesis of (S)-arogenate, a novel aryl-λ(3)-iodane-mediated oxidative spirocyclization of para-substituted phenol derivatives has been discovered. Starting from easy accessible 2-(4-hydroxybenzamido)acrylates we could construct spirocyclic lactams in up to 52% yield. Under alternative reaction conditions the same precursors underwent an unexpected oxidative spirocyclization yielding a novel δ-spirolactone in up to 70% yield.
N-[(Uracil-5-yl)methyl]urea is reported as a minimalistic low-molecular-weight hydrogelator (LMWHG). The unusual phosphate-induced assembly of this compound has been thoroughly investigated by IR, UV/Vis, and NMR spectroscopy, electron microscopy, and rheological experiments. This rare example of an anion-triggered urea-based LMWHG is the first example of a pyrimidine- and urea-containing molecule that can be forced into self-assembly in aqueous solution without additional aromatic or lipophilic groups. The gelator/phosphate ratio within the hydrogel was successfully determined by (31) P MAS NMR spectroscopy. The hydrogel exhibits a very fast and repeatable self-healing property, and remarkable G' values. The viscoelastic properties of the hydrogel can easily be tuned by variation of the phosphate ratio.
An efficient asymmetric synthesis of D-α-(uracil-5-yl)glycine derivatives using an enzymatic dynamic kinetic resolution of D,L-hydantoin intermediates with an immobilized D-hydan-
A UV light-induced photodimerization of 5-[(imidazol-1-yl)methyl]uracil using glutamate- and aspartate-derived cyclic dipeptides (2,5-diketopiperazines - DKPs) as templates was investigated. Dual salt bridge formation between imidazole side chains and carboxylic acids resulted in the preorganization of the uracil monomers and the preferential formation of the cis-syn photodimer.
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