The estimation of ν6 of octahedral XY6 species

The inactive F_2u vibration frequency of octahedral XY₆ type species for which this frequency is known, was estimated from the remaining frequencies using the Urey—Bradley (UBFF) and orbital valency (OVFF) force fields and their modifications. Various modifications of the generalized valency force field (GVFF) were also considered. Estimated values were scattered within a wide range and the average discrepancy varied from 20 (UBFF) to 68% (modified OVFF). The condition ν₆ = ν₅/√2 (Wilson's rule), with an average discrepancy of 15% gave the closest estimate of the assigned values.     

Synthesis of oligo-6-bromo-6-deoxy-β-cyclodextrins

Two methods of synthesis of oligo-6-bromo-6-deoxy--cyclodextrins, with use of the Vilsmeier-Haack reagent and via tosyl derivatives of -cyclodextrin, were compared. The second method holds more promise, since it allows a desired number of bromine atoms to be introduced into the -cyclodextrin molecule instead of hydroxy groups. A correlation between the decomposition onset points of oligo-6-bromo-6-deoxy--cyclodextrins and the number of bromine substituents in them was revealed.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1743–1745.Original Russian Text Copyright © 2004 by Kurochkina, Trushkin, Grachev, Nifantev.This revised version was published online in April 2005 with a corrected cover date.     

Isomerization of B6, B6 − and B6 + clusters

The interconversions between isomers with the same spin multiplicity of neutral B₆ and charged B₆ ^? and B₆ ⁺ clusters have been investigated at the B3LYP/6-311+G* level of theory, including determination of the minimum energy pathways with transition states connecting the corresponding reactants and products. In dynamic calculations, 26 isomers were optimized, including 11 novel isomers. In order to further refine the energies, single-point B3LYP/6-311+G(3df) calculations were carried out on the corresponding B3LYP/6-311+G* geometries of all isomers of B₆, B₆ ^? and B₆ ⁺ and the corresponding isomerization transition states. The stability of each isomer of B₆ (singlet and triplet states), B₆ ^? (doublet state) and B₆ ⁺ (doublet state) was analyzed from both thermodynamic and dynamic viewpoints.     

The Benzoylation of 6-Methyluracil and 5-Nitro-6-methyluracil

6-Methyluracil and 5-nitro-6-methyluracil react with variable molar quantities of benzoyl chloride in acetonitrile-pyridine at room temperature to give I-N, 3-N-dibenzoyl-6-methyluracil 3b and l-N-benzoyl-5-nitro-6-methyluracil 4b. The reactive rates of debenzoylation of 3b and 4b were investigated.     

A convenient synthesis of 6-demethoxycapillarisin

A convenient and effective method for the synthesis of 6-demethoxycapillarisin was described.The highlight was involved in asimple access to the key intermediate 2-ethylthio-5,7-dimethoxy-4H-chromen-4-one from the inexpensive 2,4,6-trihydroxyacetophenone,using AlCl3 as the demethylation reagent.     

First Total Synthesis of 6-Oxodendrolasinolide

~~First Total Synthesis of 6-Oxodendrolasinolide1.For a report on vinyl dithiane regioselectivity and similar reactions, see: (a) W. S. Murphy, S. Wattanasin, J. Chem. Soc, Perkin Trans. 1, 1980, 2678. (b) L. Colombo, C. Gennari, M. Santandrea, et al, J. …     

Synthesis of L‐6‐Chloropyrroloindoline of Chloptosin Cyclohexapeptide

Abstract

Chloptosin is an apoptosis‐inducing dimeric cyclohexapeptide. Enantioselective synthesis of L‐6‐chloropyrroloindoline, as the key chiral synthon of the cyclohexapeptide of chloptosin, was successfully achieved starting from 3‐chloroaniline by utilizing Fischer indole/Schöllkopf protocol and oxidative cyclization of resulting L‐6‐chlorotryptophan.     

Microwave-assisted synthesis of 6-amino-β-cyclodextrins

A general microwave-assisted procedure for the synthesis of 6-amino-β-cyclodextrins is reported. Mono-tosyl-β-cyclodextrin was used as the starting material in a one-pot route employing a solvent-free microwave-assisted reaction with a liquid amine. Shorter reaction times were observed for the formation of 6-amino-β-cyclodextrins using this novel microwave approach compared to the thermal procedure.     

Synthesis of 6β-Halogenodeoxyneopine from Neopine

(-)-Neopine (1), the Δ^8,14 isomer of codeine, occurs as one of the minor constituents in opium from Papaver somniferum L¹. In opium alkaloids of the morphine group the hydroxyl group in position 6 is readily converted with p-toluenesulfonyl chloride or methanesulfonyl chloride into the respective 6α-O-sulfonyl derivatives². The latter in turn form starting materials for the preparation of other derivatives. Thus, with lithium halides, via a S_N2 mechanism³ the 6β-halogen compounds are formed. It is found that, as a result of the allylic system, under slightly changed reaction conditions codeine itself can also yield the 8β-chloro derivative⁴.     

Studies on Kinetics of Crystallization of PA6／UFAPR Composites

The influence of Ultrafine Full-Vulcanized Acrylate Powdered Rubber(UFAPR) on the isothermal crys-tallization kinetics and nonisothermal crystallization behavior of PA8 has been studied by means of DSC. The results show that with the introduction of a small amount of UFAPR, the crystallization rate of PA8 can be increased obviously, and the crystallization temperature range can be augmented and the crystallite size distri-bution of the crystal can be narrowed down. The change of free energy perpendicular to the crystal nucleus, which has been calculated according to the Hoffman theory, is consistent with the result of Avrami′s equa-tion. The unit surface free energy of the radial-developing crystal spherulite decreases while the crystalliza-tion rate of PA8 increases with the introduction of UFAPR. Meanwhile, it is shown by means of the polariz-ing microscope(PLM) that the crystal size drops down and the number of the crystal grains augments with the addition of UFAPR, which shows that UFAPR can function as a nucleating agent.     

Synthesis of 6-chloronicotinates of steroidal 3β,5α,6β-triols and 3β,5-dihydroxy-6-ketones

New esters of 3β,5α,6β-trihydroxysteroids and 3β,5-dihydroxy-6-ketosteroids containing 6-chloropyridine groups characteristic of the alkaloid epibatidine were synthesized by acylation with 6-chloronicotinoylchloride. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 175-179, March-April, 2009.     

Influence of Cu6PS5І superionic nanoparticles on the dielectric properties of 6СВ liquid crystal

Influence of Cu₆PS₅? nanoparticles on the dielectric properties of planarly oriented 6СВ liquid crystal (LC) is studied in the 10–10⁶-Hz frequency range. Introduction of the nanoparticles is shown to result in an increase of the electric conductivity. Contrary to 6СНВТ LC, the conductivity monotonously depends on the nanoparticles’ concentration. The main reason of the much greater influence of Cu₆PS₅? nanoparticles on the 6СВ conductivity in comparison with 6СНВТ is related to a greater dissociation coefficient of Cu₆PS₅? in 6СВ than in 6СНВТ. This is confirmed by the fact that the dipole moment of the 6СВ molecules is greater than that of the 6СНВТ molecules.     

Synthesis of an Analogue of Squalamine： 6β-Hydroxyl-3-aminosterol

6β-Hydroxylsqualamine was synthesized stereoselectively in 13 steps and 19% overall yield from methyl hyodeoxycholanate by using stereospecific epoxidation and asymmetric isopropylation as key steps.     

Synthesis of 6, 9, 11-Trihydroxy-6a, 12a-dehydrorotenoid

6, 9, 11-Trihydroxy-6a, 12a-dehydrorotenoid 1 (coccineone B) was synthesized from 2-hydroxybenzaldehyde 2 and phloroglucinol.     

Synthesis of 5α-Iodo-6-one Steroids

Abstract: The synthesis of 5-iodo-5α-cholestan-6-one (6), its 3β-acetoxy-(7) and 3β-chloro-(8) analogues, 3β-acetoxy-5-iodo-5α-stigmastan-6-one (9) and its 3β-chloro-(10) analogue by the reacion of silver chromate-iodine and pyridine with the corresponding steroidal olefins (1-5) is described. The structures of these products have been established on the basis of their elemental, analytical and spectral data.     

Some derivatives of pregna-D6′-pentaranes as possible antagonists of progesterone

Some derivatives of progestins of the pregna-D₆-pentarane series have been obtained and examined for their possible hormonal and antihormonal activity in the Clauberg-McPhail assay as well as in the pregnancy maintenance test in ovariectomized rabbits. 16, 17-Cyclohexanoprogesterones of the 19-methyl and 19-nor series (1–4) saturated in ring A, which are inactive as progestins, exhibited a remarkable antiprogesterone effect. They decreased the McPhail index under combined administration with progesterone in a dose-dependable manner and completely inhibited the action of the latter in the pregnancy maintenance test.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 564–567, March, 1995.     

Crystal Structure of Mixed Sodium-Potassium Paradodecatungstate 6-Hydrate

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Synthesis of Stigmastane 5β-Hydroxy-6-ketosteroids

-Sitosterol 1 and the intermediate 5-hydroxy-6-ketosteroids 2 and 3 were used to synthesize 5-hydroxy-6-ketosteroid oximes 4 and 5. Dehydration of 5 fromCinachyrellasponges forms (24R,6E)-24-ethylcholest-6-hydroximino-4-en-3-one 6, a steroidal oxime