摘要:

A new synthesis of 2-deoxystreptamine (21), a component of numerous antibiotics, was developed. Starting fromD-mannose, it proceeds through chiral intermediates and is designed to furnish starting points for the preparation of stereospecifically modified derivatives of themesocompound21. 1,2-Dideoxy-1-nitro-D-manno-heptitol (2), obtainable from mannose by the nitromethane method, was protected as the 4,5:6,7-di-O-isopropylidene derivative4, which was mesylated or triflated in position 3. From the sulfonic esters (5and6) two different routes involving displacement by azide, partial deacetonation at O-6,7, periodate oxidation, and cyclization of the resulting nitroaldohexose derivatives converged to give 1L-(1,3/2,4,6)-6-azido-1,2-O-isopropylidene-4-nitro-1,2,3-cyclohexanetriol (19) as a key intermediate. Catalytic hydrogenation then afforded optically active 4,5-O-isopropylidene-2-deoxystreptamine (23), isolated as itsN,N′-diacetyl derivative24. Deacetonation of19gave the azidonitrotriol15, which was reduced to21. The potential utility of the chiral intermediates for stereospecific syntheses of deoxystreptamine-containing aminoglycosides is discussed.

ISSN:0008-4042    

DOI:10.1139/v87-246

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The novel ferroceneophane1c, is the product of the reaction of silicon tetrachloride with the dilithio derivative ofN,N-dimethyl-α-ferrocenylethylamine. Crystals of1care monoclinic, space groupC2/c,a = 15.275(2),b = 9.0869(4),c = 22.363(2) Å, β = 95.814(5)°,Z = 8,R = 0.037 for 2274 reflections. The tilt angle between the cyclopentadieneyl rings is 19.0(2)° and the bridge-head angle at silicon is 100.7(1)°. Other angles at silicon indicate some repulsive interaction with the CHMeNMe2group. Silica rapidly reacts with1cto give materials which have essentially the same Mössbauer spectra as the starting material.1creacts with methanol to give Fe(C5H3(CHMeNMe2)Si(OMe)3-1,2)(C5H5) and other products.

ISSN:0008-4042    

DOI:10.1139/v87-247

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Crystals of 8-methyl-6,6-diphenyl-5,7-dioxa-8-azonia-6-borata-6,7-dihydro-5H-benzocycloheptene are triclinic,a = 12.917(1),b = 13.285(1),c = 10.567(1) Å, α = 94.183(8), β = 90.094(5), γ = 72.176(6)°,Z = 4, space group. The structure was solved by direct methods and was refined by full-matrix least-squares procedures toR = 0.045 andRw = 0.042 for 2914 reflections withI ≥ 2σ(I). The envelope-like conformation adopted by the seven-membered chelate ring places oneB-phenyl group above the plane of the fused-ring system facilitating a thermally-induced 1,4-migration of aB-phenyl group to the nitrone carbon atom. Mean bond lengths (corrected for libration) are (N)O—B = 1.559(6), (C)O—B = 1.496(3), C—B = 1.610(4) Å.

ISSN:0008-4042    

DOI:10.1139/v87-248

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The thermolysis of ethyl azidoformate in acetic and propionic anhydrides as solvents yielded the correspondingN-acyl-2-oxazolidinones (2a,b) in relatively significant yields. The other major products isolated wereN-carboxyethyl-N,O-diacyl hydroxylamine (1a,b) andN,N,O-triacetyl hydroxylamine (3), The intramolecular cyclization is facilitated by the solvent.

ISSN:0008-4042    

DOI:10.1139/v87-249

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Deuterium induced isotope effects on the119Sn chemical shielding constants have been measured for stannane and the stannonium cation; they are found to be approximately −0.403 ppm/D and −0.05 ppm/D respectively. The119Sn shifts in the series SnDnH4−n(n ≤ 4) deviate from additivity as predicted by Jameson and Osten. The primary and secondary isotope effects on Sn–H spin–spin coupling for stannane were obtained and are −2.8 Hz and −1.7 Hz respectively. The primary isotope effect for Sn–H spin–spin coupling for the stannonium cation was found to be −11.6 ± 7 Hz; an accurate value for the secondary isotope effect on the spin–spin coupling could not be obtained. The derivative of the119Sn shielding constant andJ(Sn,H) with respect to extensions in the equilibrium bond length have been calculated for stannane.

ISSN:0008-4042    

DOI:10.1139/v87-250

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Enthalpies and heat capacities of solution at infinite dilution fortert-butyl chloride and bromide in several alcohols are reported at 30, 35, and 40 °C.The Scaled Particle Theory (SPT), the Sinanoglu, Reiss, and Moura Ramos (SRMR) and the Model Solute (MS) methods were applied to the enthalpies of solvation. Significant differences in the results calculated from these theories were analysed and data discussed in terms of solute–solvent–solvent interactions.

ISSN:0008-4042    

DOI:10.1139/v87-251

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The protonation constants of monomeric (TM) and dimeric (TD) forms of thymine and monomeric (OM) and dimeric (OD) forms of orotic acid and thymidine (TY) have been calculated at 25 and 37 °C and at ionic strength μ = 0.1 (NaNO3). Under the same conditions the stability constants of their Cu(II), Hg(II), and Pt(II) complexes have been determined by protometric methods. The results have been discussed and a comparison has been established in terms of binding sites: nitrogen N3 for monomeric and dimeric forms of thymine and thymidine; carboxylate anion at C6 and adjacent ring nitrogen N1 for monomeric and dimeric forms of orotic acid.

ISSN:0008-4042    

DOI:10.1139/v87-252

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Homobinuclear metal chelate complexes having 1,4-dihydroxy-9,10-anthracenedione (quinizarin) as a bridging unit have been prepared with four bivalent first row transition elements, namely cobalt, nickel, copper, and zinc. The coordination spheres of the metal ions consist of two nearly equivalent six-membered rings with oxygen donor atoms derived from the quinizarin and the terminal ligands which are either β-diketones or salicylic aldehyde. TG, spectroscopic (ir, uv–vis, epr), and magnetic measurements have been applied to an investigation of the geometry adopted by the MO4chromophores. The results are consistent with varying degrees of distortion from the ideal square planar toward a tetrahedral arrangement around the metal ions, closely related to the specific metal center involved.

ISSN:0008-4042    

DOI:10.1139/v87-253

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A patent of Benson (1980) states that a methane/chlorine flame produces some ethane and some ethylene. A fundamental study of the reaction has been carried out using an isothermal, continuous, stirred reactor operated at temperatures varying from 800 to 1000 °C, at subatmospheric pressures, at low concentrations of chlorine (about 1% by volume), and with reaction times of about 1 s. Under these conditions, the reaction leads mainly to the formation of the following carbon compounds: CH3Cl, C2H4, C2H6, and C3H6. The percentage of methane that is transformed into non-chlorinated hydrocarbons rises with the temperature and reaches a level of 77% at 1000 °C. A radical mechanism which takes into account all the data is proposed and analysed. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v87-254

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The1H nuclear magnetic resonance spectral parameters are reported for 3-phenyl-1-propyne dissolved in CCl4, C6D6, and in acetone-d6. The long-range spin–spin coupling constants imply very small and perhaps vanishing barriers to internal rotation about thebond in all three solutions, in contrast to benzyl cyanide in which there exist significant solvent perturbations of the internal barrier. STO 3G MO computations, utilizing geometry optimization procedures, imply an internal rotational potential of V/kJ mol−1 = −2.8 sin2 ψ − 0.6 sin2 2ψ; the angle ψ is 90° when the C≡C bond lies in a plane perpendicular to the benzene plane. 6-31G MO energies imply V/kJ mol−1 = −0.3 sin2 ψ − 0.4 sin2 2ψ, the fourfold component being larger than the twofold. A flat minimum occurs near ψ = 50°.

ISSN:0008-4042    

DOI:10.1139/v87-255

出版商:NRC Research Press    

年代:1987

数据来源: NRC