Novel heterocycles. 7. Reaction of 2-chloronicotinonitrile with thioureas. Synthesis of the pyrido[2,3-d]pyrimido-[2,1-b][1,3]thiazine ring system

N,N'-Dimethylthiourea and 3,4,5,6-tetrahydro-2-pyrimidinethiol were allowed to react with 2-chloro-nicotinonitrile ( 1 ) and their products investigated by standard methods and by carbon-13 nmr. In both instances, displacement of the chlorine occurred by nitrogen not the sulfur of the thioureas. Secondary cyclizations occurred by attack of nitrogen on the nitrile to furnish 3a , and by sulfur on the nitrile to give 4b , a new ring system. Tricyclic 4b was hydrolyzed in dilute acid to give 5 , or alkylated with methyl iodide in the presence of sodium hydride to give the ring opened product 6 .     

RAMPED-UP NMR: multiplexed NMR-based screening for drug discovery

The crucial step in drug discovery is the identification of a lead compound from a vast chemical library by any number of screening techniques. NMR-based screening has the advantage of directly detecting binding of a compound to the target. The spectra resulting from these screens can also be very complex and difficult to analyze, making this an inefficient process. We present here a method, RAMPED-UP NMR, (Rapid Analysis and Multiplexing of Experimentally Discriminated Uniquely Labeled Proteins using NMR) which generates simple spectra which are easy to interpret and allows several proteins to be screened simultaneously. In this method, the proteins to be screened are uniquely labeled with one amino acid type. There are several benefits derived from this unique labeling strategy: the spectra are greatly simplified, resonances that are most likely to be affected by binding are the only ones observed, and peaks that yield little or no information upon binding are eliminated, allowing the analysis of multiple proteins easily and simultaneously. We demonstrate the ability of three different proteins to be analyzed simultaneously for binding to two different ligands. This method will have significant impact in the use of NMR spectroscopy for both the lead generation and lead optimization phases of drug discovery by its ability to increase screening throughput and the ability to examine selectivity. To the best of our knowledge, this is the first time in any format that multiple proteins can be screened in one tube.     

Regioselective catalytic addition of terminal acetylenes to methyl esters of 1-alkylcyclopropene-3-carboxylic acids

Conclusions Terminal acetylenes and HCN in the presence of CuCl add regioselectively as CH-acids to the unsaturated three-membered ring of methyl esters of 1-alkylcyclopropene-3-carboxylic acids to form the methyl esters of the corresponding 3-alken-5-ynoic acids or 4-cyano-3-alkyl-3-butenoic acids in yields up to 60%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2401–2405, October, 1985.These results were partially reported at the Seventh All-Union Conference on the Chemistry of Acetylene [1].     

Crystal and molecular structure of 1-aza-6′-(3′-oxo-5′, 5′-dimethyl-δ1′-pyrrolin-3′-yl)methylidene-2,2,7,7-tetramethyl-4-hydroxybicyclo-[2.2.21azaoctane

An x-ray structural study has shown that 6-(3-oxo-5,5-dimethyl-¹-pyrrolin-3-yl)methylidene-2,2,7, 7-tetramethyl-4-hydroxybicyclo[2.2.2]azaoctane is formed as a low-molecular-weight byproduct of the solid-phase polymerization of 1,4-bis(2,2,6,6-tetramethyl-4-hydroxy-4-piperidyl)butadiyne.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 585–587, March, 1990.     

Nucleic acid analysis using an expanded genetic alphabet to quench fluorescence

Organic chemistry has made possible the synthesis of molecules that expand on Nature's genetic alphabet. Using the previously described nonstandard DNA base pair constructed from isoguanine and 5-methylisocytosine, we report a highly specific and sensitive method that allows for the fast and specific quantitation of genetic sequences in a closed tube format. During PCR amplification, enzymatic site-specific incorporation of a quencher covalently linked to isoguanine allows for the simultaneous detection and identification of multiple targets. The specificity of method is then established by analysis of thermal denaturation or melting of the amplicons. The appropriate functions of all reactions are further verified by incorporation of an independent target into the reaction mixture. We report that the method is sensitive down to the single copy level, and specificity is demonstrated by multiplexed end-point genotypic analysis of four targets simultaneously using four separate fluorescent reporters. The method is general enough for quantitative and qualitative analysis of both RNA and DNA using previously developed primer sets. Though the method described employs the commonly used PCR, the enzymatic incorporation of reporter groups into DNA site-specifically should find broad utility throughout molecular biology.     

Free azoxy radicals from benzoquinolines

Conclusions The 5,6- and 7,8-benzo derivatives of 4-methyl-2-spirocyclohexyl-3,4 3,2-tetrahydrofurano-1,2,3,4-tetrahydroquinoline and their paramagnetic N-oxides were synthesized. A study was made of the paramagnetic absorption spectra of the free radicals, which are bezoquinoline derivatives.     

Extraction of interaction potentials from the elastic scattering amplitudes: an accurate quantum mechanical procedure

A quantum-mechanical method for obtaining the interaction potential from the elastic scattering amplitude is described. We present two examples in which nonmonotonic potentials possessing deep wells and strong repulsions are accurately determined.     

Formation of unsaturated bicyclic γ-butyrolactone by oxidative dimerization of 2-methyl-2-ethynylcyclopropanecarboxylic acid

Conclusions The oxidative dimerization of a mixture of the trans and cis isomers of 2-methyl-2-ethynylcyclopropanecarboxylic acid in the presence of CuCl and NH₄Cl gives, along with bis(trans-1-methyl-2-carboxyl-1-cyclopropyl)diacetylene (53% yield), also the corresponding dilactone, and specifically bi(1-methyl-4-oxo-3-oxabicyclo[3.1.0]-2-hexalidene)methyl (14% yield), which is probably formed via the intramolecular cyclization of the intermediately formed bis(cis-1-methyl-2-carboxy-1-cyclopropyl) diacetylene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1164–1166, May, 1981.     

Steric mode of enzymic hydroxylation at primary carbon atoms: Hydroxylation of (1R)- and (1S)-[1-3H, 2H, 1H][1-14C]-octanes by Pseudomonas Oleovorans

(1R)- and (1S) [1-³H, ²H, ¹H]-octanes and mixed with [1-¹⁴C]-octane, were synthesized. The mixed samples were incubated with homogenats of P. oleovorans strain TF4-1L and the biosynthesized mixtures of octanols isolated. It was shown that mainly the achiral termini [-C¹H₃] were hydroxylated and that chiral methyls were oxygenated to the extent of 20–30%. In all instances the products derived from hydroxylation at the chiral methyls [-C-³H, ²H, ¹H] were mixtures of (1R)- and (1S)-octanols, the major component of which was the alcohol obtained by displacement of ¹H. The results indicate that hydroxylation proceeded with a normal isotope effect k_h>k_d>k_t. The amount of (1R)-octanol in the mixtures of octanols derived from (1R)- and (1S)-octane was determined. It was found that the C-1 hydroxylation of octane proceeded with retention, i.e. the incoming hydroxyl assumed the orientation of the displaced hydrogen (or isotopic hydrogen) atom.     

Affinity NMR: decoding DNA binding

We have shown that affinity NMR can be used to edit a NMR spectrum so that ligands that have affinity to DNA can be observed in the presence of other nonbinding molecules. Diffusion encoded spectroscopy (DECODES) can be used to identify the binding ligands. We were able to identify Hoechst 33342 as binding to the Drew-Dickerson dodecamer d(CGCGAATTCGCG)2 in the presence of the nonbinding molecules adenine, adenosine, and thiamine. Affinity NMR appears to be readily applicable to DNA systems for the following reasons. (1) The relaxation rate of the DNA oligonucleotides is favorable, thus the signal intensity loss due to relaxation is not severe. (2) A comparison of the patterns of the DNA cross-peaks upon binding in the two-dimensional total correlation spectroscopy and correlation spectroscopy spectrum are easily performed, and the ligand signals in the two-dimensional DECODES spectrum can be readily identified. (3) The aromatic part of the DNA spectrum is devoid of 2D cross-peaks in these correlation spectra, greatly facilitating the interpretation of the bound ligand in the DECODES spectrum.