A synthetic approach for the preparation of a new class of highly conjugated unnatural α-amino acids bearing a 5-arylpyrazole side-chain has been developed. Horner-Wadsworth-Emmons reaction of an aspartic acid derived β-keto phosphonate ester with a range of aromatic aldehydes gave β-aryl α,β-unsaturated ketones. Treatment of these with phenyl hydrazine followed by oxidation allowed the regiose...

A β-keto ester grouping is a characteristic of ring E of the chlorophylls (Chls). Its presence has also reinforced the original identification of nonfluorescent Chl catabolites (NCCs) as colorless, amphiphilic phyllobilins (PBs). Polar NCCs were also detected in higher plants, in which a free carboxyl group replaced the ring E ester group. Such NCCs are surprisingly resistant to loss of this ca...

In order to improve the water-solubility of curcumin, the complex between curcumin and hyperbranched poly(amide-ester) was formed by dispering the solid curcumin in hyperbranched poly(amide-ester) aqueous solution. The interaction process was characterized by UV-vis absorption spectroscopy, Fluorescence quenching method, Fourier transformation-infrared spectroscopy, thermogravimetric analysis. ...

The first stereoselective total synthesis of gonytolide C, which is a monomeric unit of an innate immune promoter gonytolide A, has been accomplished from the aldol reaction between acetophenone derived from orcinol and butyrolactone containing α-keto ester followed by the excellent diastereoselective intramolecular cyclization. The first total synthesis of gonytolide G has been achieved by the...

Lewis acidic zeolites are used to synthesize unsaturated dicarboxylic acid esters via aldol condensation of keto esters. Hafnium-containing BEA (Hf-BEA) zeolites catalyze the condensation of ethyl pyruvate into diethyl 2methyl-4-oxopent-2-enedioate and diethyl 2-methylene-4oxopentanedioate (an itaconic acid ester analogue) with a selectivity of ca. 80% at ca. 60% conversion in a packed-bed reac...

SYNLETT 2010, No. 11, pp 1712–1716xx.xx.2010 Advanced online publication: 14.06.2010 DOI: 10.1055/s-0030-1258094; Art ID: Y00510ST © Georg Thieme Verlag Stuttgart · New York Abstract: The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing t...

In the title compound (systematic name 1-hy-droxy-1,2-dihydro-obacunoic acid 3,4-lactone monohydrate), C(26)H(32)O(8)·H(2)O, the dihedral angles between the planes of the ester groups and the furan plane are 43.06 (12) and 56.06 (7)°, while that between the furan plane and the keto group is 58.50 (9)°. The A/B, B/C and C/D ring junctions are all trans-fused. Inter-molecular O-H⋯O hydrogen bonds...

A simple stereoselective synthesis of montroumarin [(3S)-6,8-dihydroxy-3-phenyl-3,4-dihydroisocoumarin] isolated from Montrouziera sphaeroidea has been achieved. Condensation of benzoyl chloride with 3,5-dimethoxyhomophthalic acid afforded 6,8-dimethoxy-3-phenylisocoumarin (3) which on sequential saponification and esterification yielded the keto ester 5. Enantioselective reduction of the latte...

Peripheral magnesium complexes of methyl pheophorbides a and b, bacteriomethyl pheophorbide a, bacteriopheophytin a, and protopheophytin a have been prepared and characterized by UV-vis, IR, ‘H N M R , and luminescence spectroscopy. In these compounds, Mg is bound to the peripheral p-keto ester system present in most chlorophylls rather than to the central tetrapyrrole cavity as in the chloroph...

A new synthetic approach to hexahydroisoindol4-ones is reported, based on the formal [3+2] cyclization reaction between N-arylsulfonylimines and cyclic conjugated dienes, under phosphine catalysis. Key substrates are 3-vinylcyclohex-2-enones with electronwithdrawing substituents (ester, amido, cyano, phosphoryl and keto groups) on the exocyclic double bond, which afford the three atom synthons ...