摘要:

The title cations form pseudobases in aqueous solution as shown by their uv and pmr spectra. Of the two potential pseudobases possible when the substitution is unsymmetrical, the preferred one is that having the hydroxyl group adjacent to the less bulky substituent. Aside from this steric influence, the pKROHvalues for the pseudobases are determined by simple electronic effects since they give reasonable correlations with Taft's σ* values.

ISSN:0008-4042    

DOI:10.1139/v76-380

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Nonaribonucleotide, GpCmpUpCpApUpApApC, was synthesized using a block phosphotriester method. Its sequence corresponds to that of the anticodon loop of transfer RNAfMet(E.coli). Protected tetramer, GCmUC and pentamer nucleotides, AUAAC, assembled stepwise from nucleoside derivatives, were joined together to give protected nonamer which on deblocking, gave the free nonaribonucleotide in milligram amounts. The superior internucleotide coupling efficiency of mesitylenesulfonyl triazolide (MST) over triisopropylbenzenesulfonyl chloride (TPS) is demonstrated.

ISSN:0008-4042    

DOI:10.1139/v76-381

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

A series of complexes [LM(CO)3X]R2pz = pyrazolyl, or 3,5-dimethylpyrazolyl,x = 0–2; M = Mn, X = Cl; M = Re, X = Br) andwere prepared by the reaction of the appropriate ligand with [M(CO)5X] or [M(CO)4X]2, and were characterized by elemental analysis, solution molecular weight, and infrared, mass, and nmr spectroscopic data. The products are formed via tetracarbonyl intermediates, of which the phosphorus bonded derivativewas isolated and characterized. The tricarbonyl complexes [LM(CO)3X] andadopt acis-octahedral configuration, in which the ligands form four-, five-, or six-membered chelate structures, via (i) the P atom and the 2-N site of the pyrazolyl moiety, with, (ii) the sulphur and 2-N atoms, with, (iii) the 2-N atoms of two pyrazolyl rings, withand (iv) the 2-N atoms of three pyrazolyl rings, resulting in a bicyclic system, with P(R2pz)3.The reactions of [CH3Re(CO)5] withrequire forcing conditions, resulting in the simultaneous elimination of carbon monoxide and methane, and yielding a variety of products, including tetracarbonyl, tricarbonyl, and ring-metalated species.

ISSN:0008-4042    

DOI:10.1139/v76-382

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The syntheses of P—N bonded pyrrolyl- and 2,5-dimethylpyrrolylphosphines(x = 0–2) and the oxy derivatives py3PO and (Me2py)2P(O)Cl by the reaction of potassium pyrrolide or 2,5-dimethylpyrrolide with an appropriate chlorophosphine or with POCl3are described. Molecular structures were inferred from spectroscopic data. The P—N bonded phosphines are stable to solvolytic attack by water or alcohols and do not undergo insertion reactions with CS2, but they are oxidised by oxygen and suffer nucleophilic displacement of the azole moiety by strong base. The Lewis acid BCl3cleaves the P—N bond and CH3I reacts with only one member,to form a phosphonium salt. Hindered rotation about the P—N bond was detected in the (2,5-dimethylpyrrolyl)phosphine series, but not among the corresponding oxy derivatives. The nature of the P—N bond and trends in the basicity of the phosphorus atom are discussed.

ISSN:0008-4042    

DOI:10.1139/v76-383

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The new P—N bonded phosphino- and phosphinatopyrazolesand (C2H5)2P(pz) and the arsenic derivative (pz)3As have been prepared and characterized (pz = pyrazolyl, Me2pz = 3,5-dimethylpyrazolyl).The reactivity of the P—N bond in phosphinopyrazoles towards electrophiles and nucleophiles is discussed. HCl, H2O, CH3OH, and BCl3cleave the P—N bond, presumably via attack at the 2-N site. BF3forms 1:1 adducts bonded to phosphorus which are reasonably stable in the solid state. CH3I forms a phosphonium salt with diphenyl(pyrazolyl)phosphine while other members of the series do not react. All members are inert toward CS2. Nucleophiles like sodium methoxide or phenyllithium displace the pyrazolyl moiety by attack at the phosphorus. Comparisons are made with the P—N bond in dialkylaminophosphines.

ISSN:0008-4042    

DOI:10.1139/v76-384

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The compound butaclamol hydrobromide crystallizes in space groupP21/cwith cell dimensions;a = 14.38(3),b = 13.31(3),c = 12.07(3) Å, β = 101.64(8)°. The structure was solved by Patterson methods and non-hydrogen atoms have been refined isotropically using a full-matrix least-squares to anRvalue of 0.17 for 779 observed reflections.The compound dexclamol hydrobromide crystallizes in space group P212121witha = 8.412(2),b = 24.392(7),c = 10.465(2) Å. Refinement of non-hydrogen atoms using isotropic thermal parameters and rigid aromatic rings converted atR = 0.090 using 1249 observed reflections, for the preferred enantiomorph, andR = 0.099 for the other enantiomorph.Both compounds have their hydroxy groups in the axial position, and both adopt conformations of the seven membered ring such that the C13bhydrogen atom experiences a flagpolebowsprit interaction with a hydrogen atom of C9.

ISSN:0008-4042    

DOI:10.1139/v76-385

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The structures of the title compounds have been determined by three dimensional X-ray crystal structure analysis.Crystals of anhydrous phenacylkojate are monoclinic, space groupP21/c, with unit cell dimensionsa = 9.087(4),b = 11.764(3),c = 12.714(4) Å, β = 116.57(2)°,Z = 4. The structure was solved by direct methods and refined by full-matrix least-squares toR = 0.044 for 1225 independent diffractometer observations. The crystal structure is held together by hydrogen bonding between carbonyl and hydroxyl groups andinteractions.Crystals of the sodium chloride complex are monoclinic, space group C2/c, with unit cell dimensionsa = 11.3714(6),b = 15.796(1),c = 14.487(1) Å, β = 97.241(5)°,Z = 4. The structure was solved by heavy atom and Fourier methods and comparison with the previously determined structure of the potassium iodide complex. It was refined toR = 0.040 for 1670 independent diffractometer observations. The structure closely resembles that of the potassium iodide complex (P21/n), but in C2/c, the alkali metal ion being eight co-ordinate in each. Na+—O distances are in the range 2.558–2.674 Å and thehydrogen bonded distance is 3.266 Å.

ISSN:0008-4042    

DOI:10.1139/v76-386

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Studies of the effects of solvent, concentration and temperature on the31P nmr parameters ofcis- andtrans-[PtCl2(PBun3)2] are reported. The coupling constants,1JPt–Pare markedly dependent upon all three variables but, in contrast to previous studies on non-coordination compounds, very little corresponding variation in chemical shifts is found. Results are discussed in terms of a solvent cavity model using reaction field, Stark and Macrae effects but it is concluded that a more specific model involving competitive solvation at platinum gives a better interpretation of the data.

ISSN:0008-4042    

DOI:10.1139/v76-387

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The well-known effect of the retardation of evaporation by monolayers of surfactants has been investigated by laser interferometry and the appropriate conventional apparatus. The temperature drop caused by evaporation has been calibrated for several surfactants in general use for conserving reservoir waters and for lecithins considered to be part of living membranes. Rate of ingress of oxygen has been treated in the same way. The best performance was about 60% retardation of evaporation for the molecules that pack well. The behaviour for O2ingress retardation was very similar. The lecithins were suitably permeable to be able to act as a bilamellar layer cell membrane.

ISSN:0008-4042    

DOI:10.1139/v76-388

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The steroid 17β-(4-imidazolyl)-5α-androstane-3β,11β-diamine,1a, R = H, acts as a catalyst for the hydrolysis of aryl esters. For a series of aryl acetates,2a–h, at 1 Mionic strength, logk2for1acatalyzed hydrolysis is linearly related to logk2for imidazole catalyzed hydrolysis, with only2d, 4-acetoxy-3-nitrobenzoate, deviating: at zero ionic strength, all anionic substrates show positive deviations, and a cationic substrate shows a negative deviation. This is interpreted in terms of a stringent geometrical requirement for strong electrostatic catalysis. With favorable geometry, a 1:1 electrostatic attraction can lead to a 15 fold rate enhancement (μ = 0). For a series of arylpropionate esters3a–c, rate constants for1acatalyzed hydrolysis show a small but progressive increase with increasing size of the aryl group: after correcting for substrate reactivity and electrostatic interactions, this hydrophobic effect is independent of the leaving group.1b(R = isopropyl) was prepared to determine the rate of reaction at N-3 of the steroidal imidazole ring: this is the more hindered nitrogen but also the more suitable for hydrophobic binding.1bwas markedly less reactive than1a, but showed larger hydrophobic effects. Detailed analysis suggests that the potential hydrophobic rate enhancement for the interaction of a phenanthryl group with the lower surface of a steroid is about 160-fold. This study provides guidelines for the design of enzyme models of greater catalytic efficiency.

ISSN:0008-4042    

DOI:10.1139/v76-389

出版商:NRC Research Press    

年代:1976

数据来源: NRC