Conversion of single-stranded oligonucleotides into cloned duplexes and its consecutive application to short artificial genes.

A general method to convert single-stranded, chemically synthesized oligonucleotides into cloned duplexes is described. Oligonucleotides supplied with 3'-terminal extensions that are complementary to 3'-protruding ends obtained by certain restriction enzymes can be cloned either directly or with the help of an adapter molecule into double-stranded vectors. Two methods have also been developed for consecutive cloning applications. According to these methods, the synthetic oligonucleotides (and their enzymatically prepared complementary strands) are joined, one after the other, inside a cloning vector, each joining requiring one cloning step. Synthetic genes are thus built up from oligonucleotides corresponding to only one strand of the DNA. The sequential assembly of the cloned duplex takes place in the 5' to 3' direction. Each oligonucleotide is supplied with a four-nucleotide-long 3'-terminal extension, but this sequence is eliminated when the joining takes place, leaving no limiting sequence between the oligonucleotides. The two consecutive cloning methods, the adapter and the polycloning site methods, are illustrated by the assembly of short artificial genes.     

Layered droplet microstructures in sheared emulsions: finite-size effects

We investigate the influence of confinement on the steady state microstructure of emulsions sheared between parallel plates, in a regime where the average droplet dimension is comparable to the gap width between the confining walls. Utilizing droplet velocimetry, we find that the droplets can organize into discrete layers under the influence of shear. The number of layers decreases from two (at relatively higher shear rates) to one (at lower shear rates), as the drops grow slightly larger due to coalescence. We argue that the layering and overall composition profile may be controlled by the interplay of droplet collisions (which can cause separation of droplet centers in the velocity gradient direction), droplet migration toward the centerline (due to wall effects), and droplet packing constraints. We also study the effects of mixture composition on droplet microstructure, and summarize these results in the form of a morphology diagram in the parameter space of mass fraction and shear rate. We find that formation of strings of the suspended phase (reported earlier by our group in flow-visualization studies on confined emulsions) is observed over a broad composition window. We also find a stable (nontransient) morphology wherein the droplets are arranged in highly ordered pearl-necklace chain structures.     

Stereochemical studies—76 saturated heterocycles—63 : synthesis of cis- and trans-n-methyl- and n-benzyl-4.5- and 5,6-tetramethylenetetrahydro-1,3-oxazines; an x-ray study of n-benzyl-cis-4,5-tetramethylenetetrahydro-1,-3-oxazinium- picrate

- The corresponding $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$-benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines $\text{(5a,b-8a,b)}$were synthesized from $\text{cis}$- and $\text{trans-N}$-methyl and$\text{N}$-benzyl-2- aminomethyl-1-cyclohexanols $\text{1a,b,2a,b}$, from $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$benzyl -2-hydroxymethyl-1-cyclohexylamines$\text{(3a,b,4a,b)}$ by reaction with formaldehyde. The aminoalcohols $\text{1a,2a,3a,b}$and $\text{4a,b}$ were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the $\text{cis}$ isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of $\text{N}$-benzyl-$\text{cis}$-4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate $\text{(7b)}$. determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy.     

Synthesis and stereochemistry of stereoisomeric 1,3-benzoxazino-1,3- and -3,1-benzoxazines

Partly saturated 3,1-benzoxazino[1,2-c][1,3]benzoxazines and 1,3-benzoxazino[3,2-c][1,3]benzoxazines were prepared in one-pot syntheses from different cyclic 1,3-aminoalcohols by treatment with salicylaldehyde or 5-bromosalicylaldehyde, followed by formaldehyde. The structures of tetracycles 3a and 5 were determined by means of X-ray diffraction.     

Nitration of dithieno[3,4-b:3′,2′-d]pyridine and dithieno[2,3-b:3′,2′-d]pyridine

The nitration of dithieno[3,4-b:3′,2′-d]pyridine ( 2 ) and dithieno[2,3-b:3′,2′-d]pyridine ( 3 ) has been studied. Nitration of 2 occurred in both positions of the c-fused thiophene ring, while 3 was predominantly substituted in the 2-position. The structures of the nitro derivatives were proven by extensive use of ¹H and ¹³C nmr spectroscopy.     

Cyclic sulfonium salts with S ... O interactions 2. Molecular structures with six-membered rings

1-[2-(N-methylcarbamoyl)phenyl]-3H-2,1-naphto-(1,8-d,e)-oxathiin-1-ium chloride (2), 1-[2-(N-methylcarbamoyl)-phenyl]-2-methyl-3-oxo-3H-1, 2-naphto-(1,8-d,e)-thiazin-1-ium chloride (3), 1-[8-(N-methylcarbamoyl)naphtyl]-2-methyl-3-oxo-3H-1, 2-naphto-(1,8-d,e)-thiazin-1-ium chloride (4) and 1-(8-carboxylatonaphtyl)-2-methyl-3-oxo-3H-1,2-naphto-(1,8-d,e)-thiazin-1-ium dipolar ion (5) cyclic sulfonium salts were prepared and their chemical properties investigated (spirosulfurane-formation, hydrolysis). The molecular structures obtained from x-ray diffraction can be described with a considerably distorted trigonal bipyramidal arrangement of the ligands about the sulfonium center, with O/N—S ... O=apical angles of 173.9, 164.9, 156.6, and 159.0°, as well as with S—O/N apical bond lengths of 1.648, 1.671, 1.664, and 1.682 Å. The structures exhibit relatively short S ... O close contacts with interatomic distances of 2.253, 2.448, 2.795, and 2.619 Å.     

On the reaction of dithiocarbamates with nitrogen-containing derivates of oxalic acid

Summary The action of bisimidochlorides of oxalic acid on dithiocarbamates produces 2-thioxo-3-aryl(alkyl)-4,5-diiminothiazolidines by cycloacylation. The molecular structure of 2-thioxo-3-(4-methoxyphenyl)-4,5-bis(phenylimino)-thiazolidine is confirmed by X-ray crystal structure analysis.

---

Zur Reaktion von Dithiocarbaminaten mit stickstoffhaltigen Derivaten der Oxalsäure

Zusammenfassung Bei der Einwirkung von Bisimidchloriden der Oxalsäure auf Dithiocarbaminate entstehen durch Cycloacylierung 2-Thioxo-3-aryl(alkyl)-4,5-diiminothiazolidine. Die Molekülstruktur von 2-Thioxo-3-(4-methoxyphenyl)-4,5-bis(phenylimino)thiazolidin wird durch Röntgenkristallstrukturanalyse bestätigt.

     

Saturated heterocycles. Part 216 . Synthesis,structure and ring opening of trans-perhydro-1,4-benzoxazepin-3-one derivatives

trans-Perhydro-1,4-benzoxazepin-3-ones 2a-c were synthesized and transformed to condensed-skeleton perhydro-trans-1,4-benzoxazepines 3a,b , the thiones 4a,b , the urea derivatives 5a,b , and N-acylated compounds 6a-e . Compounds 6b,d were ring-opened by hydrochloric acid in ethanol to yield trans-2-(1-carbethoxyethoxy)-1-acylaminomethylcyclohexane derivatives 7b,d . The ¹H- and ¹³C-nmr investigation and X-ray analysis of 5b and 6c,d proved that the expected N-acylated derivatives were formed and that both rings of the trans anellated compounds have a chair conformation.