Starting from enantiomeric pure 1-[(3S,5R)- and 1-[(3R,5S)-3-(hydroxymethyl)-2-methylisoxazolidin-5-yl]-5-methylpyrimidine-2,4(1H,3H)-diones (-)7a and (+)7b, obtained by lipase-catalyzed resolution, pure diethyl{[(3S,5R)-2-methyl-5-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)isoxazolidin-3-yl]methyl}phosphonate (-)12a and diethyl{[(3R,5S)-2-methyl-5-(5-methyl-2,4-dioxo-3,4-dihydropyrimidi...

Alkylmalonic esters, which have been recognized as important intermediates in the syntheses of various carboxylic acids, amino acids, etc., can be obtained by a variety of methods.1) Excepting the introduction of tertiary alkyl groups, the alkylation of malonic esters with alkyl halides in basic conditions, for example, in ethanol in the presence of sodium ethoxide, is one of the most important...

ÐKnoevenagel condensation between 3-nitro-2-pyridinecarbaldehyde and diethyl malonate catalyzed by titanium(IV) chloride gave diethyl 3-nitro-2-pyridylidenemalonate which was oxidized with peracetic acid to give corresponding 1-oxide. Reaction of the latter with diethylamine in the presence of primary and secondary alcohols resulted in the reduction of the nitro group and the oxidation of the v...

Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched α,β-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-2-phosphonate dimethylhydrazone, contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condens...

Two palindromic DNA sequences were analyzed with respect to their chemical reactivities with diethyl pyrocarbonate. In negatively supercoiled plasmid templates enhanced N7 carbethoxylation was found with individual purines located in presumptive single-stranded loops of DNA cruciform structures. No enhanced reactivity at these positions was observed in linear, relaxed or low superhelical densit...

In the title compound, C(14)H(18)O(6), a crystallographic center at the centroid of the aromatic ring generates the complete mol-ecule which is planar within 0.085 (1) Å for the non-H atoms. In the crystal, weak C-H⋯O and C-H⋯π inter-actions link the molecules.

Mol-ecules of the title compound, C(11)H(17)O(4)P, are linked into chiral helical chains along the crystallographic b axis via O-H⋯O hydrogen bonds between the hydr-oxy group and an O atom of the phospho-nate group. One ethyl group is disordered over two positions; the site occupancy factors are ca 0.7 and 0.3.

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...

In the title compound, [Zn(C(7)H(7)N(4)O(2))(2)(C(4)H(13)N(3))]·2H(2)O, the Zn(II) ion is penta-coordinated by three N atoms of the diethyl-enetriamine ligand and one N atom of each of the two theophyllinate anions in a distorted trigonal-bipyramidal geometry. The Zn-N distances range from 2.076 (3) to 2.221 (3) Å. The crystal packing is stabilized by O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds invol...

A new method is described for the rapid preparation of apolipoproteins for polyacrylamide gel electrophoresis. It is suitable for all serum lipoproteins including chylomicrons. The procedure involves extraction with diethyl ether in the presence of trichloroacetic acid and sodium deoxycholate. The method gives an improved protein recovery, in particular with chylomicrons. In addition, samples d...