Volume 38, Issue 9

Fluorapatite Ca 5 F(PO 4 ) 3 can be synthesized by melting of CaF 2 together with Ca 3 (PO 4 ) 2 at 1660 °C in the molar ratio CaF 2 · 3 Ca 3 (PO 4 ) 2 . Fluorapatite is more resistant against acids than hydroxylapatite Ca 5 OH(PO 4 ) 2 and can activate the remineralisation in dental enamel. The apatite of dental enamel is more resistant against mechanical stress than synthetic apatite due to a different microstructure of the crystal grains.

The compounds ZrCu 2 P 2 , YZnCuP 2 , LaZnCuP 2 , and CeZnCuP 2 have been prepared and their structures have been determined. They are isotypic and crystallize trigonally in the CaAl 2 Si 2 -type structure (space group P3̄̄m 1) with the lattice constants: ZrCu 2 P 2 a = 381,2(1) pm, c = 617,1(2) pm, YZnCuP 2 a = 398,3(1) pm, c = 652,3(2) pm, LaZnCuP 2 a = 408,2(1) pm, c = 674,2(2) pm, CeZnCuP 2 a = 406,4(1) pm, c = 669,7(2) pm. The compounds ALiCu 2 P (A=Y, Ce, Sm, Tb, Yb) crystalizze trigonally, too, in a very similar structure with the following lattice constants: YLiCuP 2 a = 398,5(1) pm, c = 657,0(2) pm, CeLiCu 2 P 2 a = 404,2 (1) pm, c = 671,8 (2) pm, SmLiCu 2 P 2 a=401,4 (1) pm, c = 663,4 (2) pm, TbLiCu 2 P 2 a = 399,4 (1) pm, c = 656,3 (2) pm, YbLiCu 2 P 2 a = 396,0 (1) pm, c = 648,4 (2) pm.

A series of tetrathio-spiro-phosphonia tetrachloroborates have been synthesized by the reaction of PCl 4 +BCl 4 - with 1,2-ethane-, 1,2-propane-and 1,3-propane dithiole. The crystal structure of 1,4,6,9-tetrathio-5-phosphonia-spiro(4,4)nonane tetrachloroborate, 3a, was determined from diffractometer data and refined to R = 0.056 for 4003 independent reflexions. 3a, orthorhombic, Pbcn, a = 1493.0(3), b = 1515.6(3), c = 1213.3(4) pm. The unit cell containes eight formula units.

Crystals of Sn 4 (N t Bu) 4 (1) are monoclinic, space group P2 1 /c, with cell constants a = 1038.9(4), b = 1468.3(5), c = 1698.8(5) pm, β = 91.6(1)° and Z = 4, while those of Sn 4 (N t Bu) 3 O (2) are triclinic, space group P 1̄, with dimensions a = 1293.0(5), b = 1027.1(5), c = 1716.7(9) pm, α = 90.9(1), β = 102.5(1), γ = 107.0(1)° and Z = 4. The molecules 1 are held together by van-der-Waals forces, whereas two molecules 2 interact in the crystal by weak 0→Sn donor bonds (290-332 pm) forming dimers. The outstanding structural elements of 1 and 2 are the Sn 4 N 4 and Sn 4 N 3 O polyhedra, which can be described by two interpenetrating tetrahedra of tin atoms and of nitrogen or nitrogen and oxygen atoms forming a distorted cube, which approaches 4̄3 m symmetry in the case of 1 and 3m for 2. Characteristic distances are in 1: Sn-N 220.2 pm, in 2: Sn-N 221.3 pm and Sn-O 213.2 pm. An almost ionic bonding model and two covalent models are discussed on the basis of the structural data including Sn 4 (N t Bu) 3 OAlMe 3 .

Reaction of tri-tert-butyl(dihalomethyl)silanes (halo = chloro, bromo) with organolithium compounds, by lithium/halogen or lithium/hydrogen exchange, leads to the corresponding carbenoids which by lithium halide elimination could give the carbenes (t-C 4 H 9 ) 3 SiCX. Further intermolecular or intramolecular reaction of these reactive intermediates provides a variety of crowded molecules including alkyltri-tert-butylsilanes, 1,2-bis(tri-tert-butylsilyl)- substituted ethanes and ethenes and ring substituted 1,2-di-tert-butyl-1-silacyclo-butanes. An X-ray structure determination of (E)-1,2-bis(tri-tert-butylsilyl)-1,2-dichloroethene reveals neither a twisting nor an elongation of the CC double bond, but the C = C-Si bond angles exhibit rather unusual values (up to 137.7°) and the Si-C (sp 2 ) bonds are as long as 195 pm. Tri-tert-butylisopropylsilane was prepared by a two step procedure and characterized by its variable temperature NMR spectra. The attempted synthesis of tetra-tert-butylsilane by reactions of the compound with bromine followed by treatment with methyllithium afforded only tri-tert-butylisopropenylsilane.

The title compound reacts with cyanogen halides, XCN (X = Br or I) to give the complexes L2(X)(CN)Ni (L = P(OPh) 3 , X = Br or I). The oxidative addition of (SCN) 2 and (SeCN) 2 to the same compound results in the formation of L 2 Ni(XCN) 2 (X = S or Se). All the complexes have been characterized by elemental analysis, and IR, 1 H NMR and electronic spectra.

The electron diffraction pattern of the vapor from a sample of SeCl 4 has been recorded with a reservoir and nozzle temperature of about 175 °C. The gas jet was found to consist of SeCl 2 (80%) and Cl 2 (20%). The bond distance in SeCl 2 is r a (Se-Cl) = 2.157(3) Å, the valence angle <ClSeCl = 99.6(5)°.

Alkyldifluorophosphites, ROPF 2 (R = p-substituted benzyl group, neopentyl, 1-adamantyl) have been obtained by a new method, involving reaction of the appropriate alkyl trimethylsilylether, ROSiMe 3 with chlorodifluorophosphine, PF 2 Cl. Reactions of these difluorophosphites with platinum(II) complexes of the type [L 2 PtCl 2 ] (L = PEt 3 , PPh 3 ) led to products such as trans-[L 2 PtCl(POF 2 )] and {[p-XC 6 H 4 CH 2 PPh 3 ] + } 2 [Pt(POF 2 ) 4 ] 2- , (X = H, Me, Cl, NO 2 ). The ease of carbon-oxygen cleavage in ROPF 2 is characteristically related to the nature of the leaving group, R.

A series of dihalo palladium and platinum complexes X 2 PtL 2 (X = Cl, I) with aminosugars L = 2-amino-2-deoxy-1,3,4,6-tetra-O-acetyl-β-D-glucopyranose, 1-O-methyl-2-amino-2-deoxy-4,6-O-benzyliden-a,β-D-glucopyranoside, 1-O-methyl-2-amino-2-deoxya-α,β-D-glucopyranoside, 6-amino-6-deoxy-1,2:3,4-di -O-isopropyliden-a-D-galactopyranose has been prepared and characterized by their IR, 1 H and 13 C NMR spectra. Monosaccharides and aminomonosaccharides have been attached to the complex via the carboxy group of α-amino acid Pt II complexes to give esters or amides with the monosaccharides as the alcohol or amine components, respectively.

Neutral 1-tert-butyl-2-methyl-Δ 3 -1,2-azaboroline and 2-methyl-1-trimethylsilyl-Δ 3 -1,2- azaboroline act as 4π electron donors in the mixed sandwich complexes 1-tert-butyl-2-methyl-η 4 -1,2-azaboroline-η 5 -cyclopentadienyl cobalt (1) and 2-methyl-1-trimethylsilyl-η 4 -1,2-azaboroline-η 5 -cyclopentadienyl cobalt (2), respectively. They are formed by the reaction of (C 5 H 5 )Co(C 2 H 4 ) 2 with the free ligands without any solvent and are isolated as green oily liquids. 1 and 2 can be transformed into mixed sandwich complexes with η 5 -1,2- azaborolinyl ring ligands by loss of a hydrogen atom of the CH 2 group. This occurs at room temperature to give 1-tert-butyl-2-methyl-η 5 -1,2-azaborolinyl-η 5 -cyclopentadienyl cobalt (3) and 2-methyl-1-trimethylsilyl-η 5 -1,2-azaborolmyl-η 5 -cyclopentadienyl cobalt (4) in low yields. Mass, 1 H, and 11 B NMR spectra are discussed.

Sensitized photooxidation of imidazoles in aqueous solution and in the presence of inorganic phosphate afforded organic phosphates with yields up to 30%. The major phosphorylated product of oxidation of 2-methylimidazole was isolated and identified as the monophosphate of 4,5-dihydroxy-2-methylimidazoline with pK a values of 2.0, 5.2, and 9.8. The compound is energy rich in aqueous solution and hydrolyses in alkaline or neutral solutions irreversibly (ΔH hyd = -9.8 kcal/mole). For the hydrolysis at pH 7 an activation-enthalpy of 25 kcal/mole and -entropy of 8 cal/deg.mole was observed. Be 2+ ions catalyse the hydrolysis.

The effects of polar solvents and proton donors on various photoreactions of the benzene ring with electron-acceptor alkenes and alkynes are described and discussed in relation to the various electronic excitation mechanisms involved. Proton donors prove valuable as mechanistic probes for polar intermediates in such processes, and can in some systems both initiate and divert reaction pathways.

Vanadocene (Cp 2 V) was reduced with potassium metal in tetrahydrofuran (THF) to give a 1:1 adduct K[Cp 2 V] which has been isolated as [K(THF)(Et 2 O)][Cp 2 V]. The reactions of this compound with various molecules (L) capable of functioning as ligands were investigated. They cause the liberation of KCp and the formation of several new organovanadium compounds. The products of these reactions were: [K(THF) 2.5 ][CpVC 8 H 12 ] for L = butadiene (C 4 H 6 ), [K(THF) 1.5 ][CpVC 6 H 5 P(C 6 H 5 ) 2 ] for L = P(C 6 H 5 ) 3 , CpV(C 4 H 6 )P(CH 3 ) 3 for L = mixture of C 4 H 6 and P(CH 3 ) 3 . Vanadocene was reacted with allyllithium to yield LiCp and [LiTMEDA][CpV(C 3 H 5 ) 2 ] (TMEDA = (CH 3 ) 2 NCH 2 CH 2 N(CH 3 ) 2 ), which was transformed via allylbromide to CpV(C 3 H 5 ) 2 . Structures and reactivities of these new organovanadium complexes are discussed.

The addition-cyclocondensation reactions of three β-hydroxyketones with four dialkyl phosphites gave 2-alkoxy-3-hydroxy-1,2-oxaphospholane-2-oxides (“α-hydroxyphostones”) (7), in moderate yields. In the solid state and in solution, these compounds exist as dimers with hydrogen bonding between the hydroxyl group and the phosphoryl oxygen atom of an adjacent molecule. The crystal and molecular structure of 3-hydroxy-2-methoxy-3,5,5-trimethyl-1,2-oxaphospholane-2-oxide (7 a) has been determined by single-crystal X-ray crystallography: C 7 H 15 O 4 P, monoclinic space group P2-1/n, cell dimensions a = 8.087(1) Å, b = 13.386(2) Å, c = 9.306(1) Å, V = 1007.4 Å 3 , Z = 4, final R = 0.052. The five-membered ring is puckered, with the carbon bearing the OH and CH 3 groups lying out of the plane of the remaining four atoms in the ring. The doubly bonded oxygen attached to the phosphorus atom and the hydroxyl oxygen are in a cis-relationship. The O(1)-O(4) intermolecular bond distance of 2.75 Å suggests hydrogen bonding. The O(1)-H(1) intermolecular bond distance of 1.97 Å is consistent with this conclusion.

The two longest wavelength electronic transitions of the quinhydrones 1 and the dependence of transition energies and intensities on the mutual orientation of hydro-quinone and p-benzoquinone is studied within semiempirical π-theory. The results are in good agreement with the experimental UV-VIS spectra of closely related cyclophane-quinhydrones. The study is extended to the yet unknown quadruple-layered systems 2 which consist of two quinhydrone moieties.

From the roots of Cassia multijuga 1:3-dihydroxy-2-methyl anthraquinone, 1:3:8-tri-hydroxy-6-methoxy-2-methyl anthraquinone, 1:8-dihydroxy-6-methoxy-2-methyl an-thraquinone-3-O-rutinoside and 1:8-dihydroxy-2-methyl anthraquinone-3-O-rutinoside have been isolated and their structures elucidated.

In order to test the effect of selenium on the anticancer activity of alkylating drugs, Seleno-TEPA (4), the selenium analog of the clinically used Thio-TEPA (1) was tested in vivo against the lymphocytic P 388 and lymphoid L1210 murine leukemias. Compound 4 is more active against P 388 leukemia than against L1210, and appears to be active over a narrower concentration range than Thio-TEPA (1). Compound 4 is less active against P 388 leukemia than 1, as evidenced by the T/C values of 164 for 4 and 239 for 1 at a dose of 4.2 mg/kg. The activity of 4 was also evaluated on the HL60 and K 562 human cell lines. Under the conditions of the cell colony assay technique, Seleno-TEPA (4) is less effective than Thio-TEPA (1).

The spin labeled analog, SL-O-TT (2), of Thio-TEPA (1) inhibits the incorporation of 3 H-thymidine by 50% (IC 50 ) at a dose of 2.6 × 10 -4 M in L 1210 and at a dose of 6 × 10 -4 M in P 388 murine leukemias. On the basis of cell fractionation studies, compound 2 was found to bind about qeually to the cell nuclei, microsomes, and mitochondria. ESR experiments indicate different of immobilization of the label in various fractions. The efficiency of binding of 2 to cells appears to be at least 6%.

Taking into consideration the known mechanism of the drug action of cyclophosphamide (1), several analogs and related compounds 5, 6, 7, 9, 11, 12 and 27 were synthesized, and tested against lymphocytic leukemia P 388 in mice. Moderate to high activity was found with 5 (T/C × 100 = 243 at a dose of 300 mg/kg), 7 (T/C × 100 = 155 at a dose of 55 mg/kg). None of these compounds was found to be more active than 1 (T/C × 100 = 339 at a dose of 65 mg/kg). Although the essential position C 4 for the enzymatic activation is completely blocked in 5, the compound possesses a high degree of activity. This result justifies a reevaluation of the proposed mechanism of drug action of 1 and its analogs.

The title compounds (1) are obtained in quantitative yield from the reaction between dppePtCl 2 (2) and alkynyl stannanes (CH 3 ) 3 Sn - C ≡ C-R (3) or (CH 3 ) 2 Sn(C ≡ C-R) 2 (4) in boiling tetrahydrofurane. The complexes 1 have been characterised by multinuclear NMR ( 13 PC, 31 P, 195 Pt).

The η 2 -ketenyl compound reacts with tetrabutylammonium cyanide forming an anionic η 2 -ketenyl complex.