Copper helices

The submitter used an insulated column with a 38 by 1.1 cm. section packed with H-in. copper helices made of No. 26 B S gauge copper wire. He states that a column packed with glass helices is unsatisfactory. The checkers used a 100 by 1.7 cm. Vigreux column. Either type of column shorfld be equipped with a total condensation, partial take-off head. 

Copper(I) tends towards a tetrahedral coordination geometry in complexes. With 2,2 -bipyr-idine as a chelate ligand a distorted tetrahedral coordination with almost orthogonal ligands results. 2,2 -Bipyridine oligomers with flexible 6,6 -links therefore form double helices with two 2,2 -bipyridine units per copper(I) ion (J. M. Lehn, 1987,1988). J. M. Lehn (1990 U. Koert, 1990) has also prepared such helicates with nucleosides, e.g., thymidine, covalently attached to suitable spacers to obtain water-soluble double helix complexes, so-called inverted DNA , with internal positive charges and external nucleic bases. Cooperative effects lead preferentially to two identical strands in these helicates when copper(I) ions are added to a mixture of two different homooligomers. 

Coughtrey, P. J. and Martin, M. H. (1977). The uptake of lead, cadmium and copper by the pulmonate mollusc, Helix aspersa Muller and its relevance to the monitoring of heavy metal contamination of the environment, Oecologica, 27, 65-74. 

In 1847 E. Harless discovered the presence of copper in the blood of the octopus Eledone and the snail Helix pomatia (172, 173). Investigation of the phenomenon by which the blood and tissues of certain marine animals turn blue on exposure to air finally led to the discovery that the blood plasma of such animals contains copper combined with a protein. Because of its analogy to hemoglobin and its ability to carry oxygen, L. Fredericq in 1878 named the copper-containing protein in the blood of Octopus vulgaris hemocyanin (173, 174). 

To a large bottle are added 116.5 gm (1.0 mole) of 3-chloro-l-hexyne, 20.0 gm (0.20 mole) of cuprous chloride, 16.0 gm (0.30 mole) of ammonium chloride, 10 ml of concentrated hydrochloric acid, 50 ml of water, and 0.6 gm of copper bronze. The bottle is sealed and shaken at room temperature for 14 days. The organic layer is separated, dried over potassium carbonate, and fractionally distilled through a glass-helix-packed column to afford 61.0 gm (52%) of nearly pure l-chloro-l,2-hexadiene, b.p. 54°-57°C (50 mm), p5 1.4567-1.4680, 9.3 gm (8%) of 3-chloro-l-hexyne, and some polymeric material. Shorter periods of reaction give lower yields. The product is purified as described for bromopropadiene. 

During the 1980s several laboratories prepared and investigated double-stranded helical complexes, systems containing either pyirolic ligands [75, 76] and derivatives [77-79] (with Zn2+, Ag+, Cu+) or oligomers of 2,2 -bipyridine [80, 81]. Helicates [80-84] may consist of up to five copper centers and these systems are reminiscent of the DNA double helix. 

After many attempts with various linkers, we found that 1,10-phenanthroline nuclei connected via their 2-positions by a -(CH2)4- linking unit will indeed form a double helix when complexed to two copper(I) centers. In addition, by introducing appropriate functions at the 9-positions, the strategy of Figure 14 could be followed to achieve the synthesis of a molecular knot of the (D) type. The precursors used and the reactions performed are represented in Figure 16. 

We realized that improvement in the yields of trefoil knots would be determined by (i) the proportion of double helix precursor formed compared with face-to-face open chain complex (Figure 18) (ii) the spatial arrangement of the four reacting ends of the helical dinuclear complex. This latter factor will reflect the extent of winding of the two molecular strings interlaced around the copper atoms. The various complexes synthesized and studied are depicted in Figure 21 [96]. 

Our template synthesis of knots implies that the target molecules are obtained as cationic dicopper(I) complexes. Therefore we considered the possibility of interconverting both enantiomers into a pair of diastereomeric salts [137, 138] by combining them with an optically active anion. Binaphthyl phosphate (BNP") [139] drew our attention because its chirality arises from the binaphthyl core, which is twisted. This helical structure is of the same type as that of die copper double helix, precursor of the knot. Besides, both compounds are aromatic and, thus, we could expect some potentially helpful stacking interactions [87],... 

To introduce the chiral auxiliary, a labile anion, unlike the classical BFJ or PF which cannot be exchanged, is required. Preliminary studies showed the triflate to be appropriate. We introduced it during the formation step of the double helix. One equivalent of copper ) triflate was added to the bischelating diphenolic strand in a reductive medium. H NMR showed that the dinuclear copper dou-... 

Starting at the far left, we see a water molecule, two common amino acids, alanine and tryptophan, a segment of a DNA double helix, a segment of a protein single helix, and the folded polypeptide chain of the enzyme copper, zinc superoxide dismutase or SOD. 

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