Studies of nucleosides and nucleotides—XLV Purine cyclonucleosides.-12. Synthesis of adenine cyclonucleosides having 8,5′-0-anhydro linkage

A cyclonucleoside having an 8,5′-0-anhydro linkage was first synthesized by treatment of 8-bromo-2′-3′-O-isopropylideneadenosine with sodium hydride in dioxan at room temperature. The cyclonucleoside (III) has UV absorption properties similar to those reported for other 0-cyclonucleosides and shows a large positive Cotton curve in ORD and CD.

When compound III was heated in N H₂SO₄, 8-oxyadenosine (IV) and 8,5′-anhydro-8-oxyadenosine (V) were obtained. Heating III in 0·1N H₂SO₄ gave 5-(adenyl-8)-D-ribose (VI). Treatment of III with sodium hydride in DMF gave a nucleoside having an exocyclic methylene (VII).

Compound III was also reacted with potassium thiocyanate, sodium azide and hydrogen sulfide. In each case the nucleophiles attacked at C⁵′ and gave 5′-substituted 8-oxyadenosine.     

Terpenoids and related compounds—IX Molecular rearrangements involving glutenols

The molecular rearrangements of glutenols on treatment with phosphorus pentachloride and phosphorus oxychloride and pyridine as well as on solvolysis of the corresponding tosyl derivatives have been investigated. Glut-5-en-3β-ol (Ia) and glut-5(10)-en-3-ol (IId) gave diene A (III). Glut-5-en-3-ol (Id) gave diene B (VII) and glut-5(10)-en-3β-ol (IIa) gave diene C (XIII) by ring contraction.     

Structural, spectral and thermal studies of N-2-(4-picolyl)- and N-2-(6-picolyl)-N′-(2-chlorophenyl)thioureas and N-2-(6-picolyl)-N′-(2-bromophenyl)thiourea

N-2-(4-picolyl)-N′-2-chlorophenylthiourea, 4PicTu2Cl, monoclinic, P2₁/c, a=10.068(5), b=11.715(2), β=96.88(4)°, and Z=4; N-2-(6-picolyl)-N′-2-chlorophenylthiourea, 6PicTu2Cl, triclinic, P-1, a=7.4250(8), b=7.5690(16), c=12.664(3) Å, =105.706(17), β=103.181(13), γ=90.063(13)°, V=665.6(2) ų and Z=2 and N-2-(6-picolyl)-N′-2-bromophenylthiourea, 6PicTu2Br, triclinic, P-1, a=7.512(4), b=7.535(6), c=12.575(4) Å, a=103.14(3), β=105.67(3), γ=90.28(4)°, V=665.7(2) ų and Z=2. The intramolecular hydrogen bonding between N′H and the pyridine nitrogen and intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen, as well as the planarity of the molecules, are affected by the position of the methyl substituent on the pyridine ring. The enthalpies of fusion and melting points of these thioureas are also affected. ¹H NMR studies in CDCl₃ show the NH′ hydrogen resonance considerably downfield from other resonances in their spectra.     

The nature of the structure difference between light and heavy water and the origin of the solvent isotope effect—I

The observed differences in heat content, entropy and free energy of light and heavy liquid water can be calculated within experimental error from measured infrared frequencies, using a model for water with tetrahedral hydrogen bonding and treating the hindered rotations (librations) of the water molecules as three-dimensional isotropic harmonic oscillators. The origin of the solvent isotope effect for monatomic ions in light and heavy water is their effect on the structure difference between light and heavy water. The quantity Δθ = h Δν/k provides a measure of this structure difference, where Δν is ν−ν′, the difference in average values of the librational frequencies of H₂O and D₂O, and ν′=ν/1·3815. Differences in heat content, entropy and free energy for solution of monatomic ions in light and heavy water and individual ionic activity coefficients can be calculated from Δθ. Hydronium and hydroxide ions are also discussed.     

Synthesis, crystal structure and third-order non-linear optical property of heterobimetallic cluster compound [MoOICu3S3(2,2′-bipy)2]

Nest-shaped cluster [MoOICu₃S₃(2,2′-bipy)₂] (1) was synthesized by the treatment of (NH₄)₂MoS₄, CuI, (n-Bu)₄NI, and 2,2′-bipyridine (2,2′-bipy) through a solid-state reaction. It crystallizes in monoclinic space group P2₁/n, a=9.591(2) Å, b=14.820(3) Å, c=17.951(4) Å, β=91.98(2)°, V=2549.9(10) ų, and Z=4. The nest-shaped cluster was obtained for the first time with a neutral skeleton containing 2,2′-bipy ligand. The non-linear optical (NLO) property of [MoOICu₃S₃(2,2′-bipy)₂] in DMF solution was measured by using a Z-scan technique with 15 ns and 532 nm laser pulses. The cluster has large third-order NLO absorption and the third-order NLO refraction, its ₂ and n₂ values were calculated as 6.2×10⁻¹⁰ and −3.8×10⁻¹⁷ m² W⁻¹ in a 3.7×10⁻⁴ M DMF solution.     

Crystal structure of 3-diethylaminomethyl-2,2′-biphenol

Crystals of 3-diethylaminomethyl-2,2′-biphenol were examined using X-ray diffraction and FT-IR spectroscopy. Their space group is P2₁/c with a=7.305(1), b=13.816(2), c=29.232(4) Å, β=92.411(3)° and Z=8. The unit cell contains two symmetry-independent zwitterions. The hydrogen atom of the protonated diethylaminomethyl group is linked to the negatively charged phenolate oxygen atom, which in turn is linked to the hydroxyl group by a short hydrogen bond (molecule a: NO=2.604(3), OO=2.512(3) Å; molecule b: NO=2.593(4), OO=2.489(4) Å). The OHO⁻H⁺N bifurcated intramolecular hydrogen bonds are crystallographically asymmetric. The IR spectrum of the crystals confirms very well the results obtained by the X-ray study. Instead of continuous absorption, only broad bands are found indicating relatively low proton polarisability in the two types of intramolecular hydrogen bonds.     

Constituents of Casimiroa edulis Llave et Lex.—VI 2′,5,6-Trimethoxyflavone, 2′,5,6,7-tetramethoxyflavone (zapotin) and 5-hydroxy-2′,6,7-trimethoxyflavone (zapotinin)

Experiments are described which show that a substance isolated from the root bark of Casimiroa edulis Llave et Lex. is 2′,5,6-trimethoxyflavone (IIa). It is demonstrated that zapotin and zapotinin, isolated previously from the same plant, are very probably 2′,5,6,7-tetramethoxyflavone (IIIa) and 5-hydroxy-2′,5,6-trimethoxyflavone (IIIb), respectively. The occurrence in nature of flavonoids of type IIa, IIIa and IIIb bearing a single oxygen substituent in ring B at the 2′-position is unusual.     

Transformations of kurchi alkaloids—I The action of nitrous acid on holarrhimine

Holarrhimine (I), 18-hydroxy-3β,20-diamino-5-pregnene, was treated with nitrous acid under different conditions. From the reaction mixtures several crystalline products were isolated and characterized as 3β-hydroxy-18-20β-oxido-5-pregnene (II), the nitrate ester of II (III), 3β-nitro-18-20β-oxido-5-pregnene (IV), 6-methoxy-18-20β-oxido-3,5-cyclopregnane (V) and 3β,18-dihydroxy-20-amino-5-pregnene (VII). On treatment with boron trifluoride and acetic anhydride compounds II, IV, V and an unidentified compound (VI) gave the same triacetate 3β,18,20-triacetoxy-5-pregnene (VIII).     

Oligomeric flavanoids. Part 13. Synthesis of profisetinidins based on (−) robinetinidol and (+) -epifisetinidol

Acid-catalyzed condensation of (+)-mollisacacidin-[(2R, 3S, 4R)-2, 3-trans-3, 4-trans-flavan-3,3′,4,4′,7-pentaol] with an excess of (−)-robinetinidol[(2R,3S)-2,3-trans-flavan-3,3′,4′,5′,7-pentaol] afforded a novel series of bi-, tri-, and tetraflavanoid profisetinidins. They are accompanied by (−)-fisetinidol-(4,2′)-(−)-robinetinidol which results from the pyrogallol B-ring of (−)-robinetinidol serving as nucleophile competing with its resorcinol A-ring in coupling with a C-4 carbocationic intermediate. Similar condensation with (+)-epifisetinidol[(2S,3S)-2,3-cis-flavan-3,3′,4′,7-tetraol] led to the exclusive formation of [4,6]-interflavanyl bonds, these units being ‘linearly’ arranged in the tetraflavanoid analogue in contrast to the ‘branched’ nature of the (−)-robinetinidol homologue.     

Recent studies on metal and metalloid bis(trimethylsilyl)methyls and the transformation of the bis(trimethylsilyl)methyl into the azaallyl and β-diketinimato ligands

Recent results (post-1990) on the synthesis and structures of bis(trimethylsilyl)methyls M(CHR₂)_m (R = SiMe₃) of metals and metalloids M are described, including those of the crystalline lipophilic [Na(μ-CHR₂)]_∞, [Rb(μ-CHR₂)(PMDETA)]₂, K₄(CHR₂)₄(PMDETA)₂, [Mg(CHR₂)(μ-CHR₂)]_∞, P(CHR₂)₂ (gaseous) and P₂(CHR₂)₄, [Yb(CHR₂)₂(OEt₂)₂] and [{Yb(CR₃)(μ-OEt)(OEt₂)}₂]; earlier information on other M(CHR₂)_m complexes and some of their adducts is tabulated. Treatment of M(CHR₂) (M = Li or K) with four different nitriles gave the X-ray-characterized azaallyls or β-diketinimates , and (LL′ = N(R)C(^tBu)CHR, L′L′ = N(R)C(Ph)C(H)C(Ph)NR, LL″ = N(R)C(Ph)NC(H)C(Ph)CHR, R = SiMe₃ and Ar = C₆H₃Me₂-2,5). The two lithium reagents were convenient sources of other metal azaallyls or β-diketinimates, including those of K, Co(II), Zr(IV), Sn(IV), Yb(II), Hf(IV) and U(VI)/U(III). Complexes having one or more of the bulky ligands [LL′]⁻, [L′L′]⁻, [LL]⁻, [LL″]⁻, [L″L]⁻, [LL]⁻ and [{N(R)C(^tBu)CH}₂C₆H₄-2]²⁻ are described and characterized (LL = N(H)C(Ph)C(H)C(Ph)NH, L″L = N(R)C(^tBu)C(H)C(Ph)NR, LL = N(R)C(^tBu)CHPh). Among the features of interest are (i) the contrasting tetrahedral or square-planar geometry for and , respectively, and (ii) olefin-polymerization catalytic activity of some of the zirconium(IV) chlorides.     

Crystal structure of Schiff base derivative of 2,2′-dihydroxybiphenyl-3-carbaldehyde with n-butylamine

Crystals of the Schiff base derivative of 2,2′-dihydroxybiphenyl-3-carbaldehyde with n-butylamine were examined using X-ray diffraction, FT-IR and CPMAS spectroscopy. Their space group is with a=8.377(2), b=12.214(2), c=14.774(3) Å, =76.62(3)°, β=81.34(3)°, γ=86.62(3)° and Z=4. The unit cell contains two symmetry-independent zwitterions. The hydrogen atom of the protonated N atom of the Schiff base is linked to the oxygen atom of the carbonyl group at position 2, which in turn is linked to the hydroxyl group by a short hydrogen bond [molecule A: NO=2.614(3), OO=2.520(3) Å; molecule B: NO=2.594(4), OO=2.526(3) Å]. The OHO⁻H⁺N bifurcated intramolecular hydrogen bonds are crystallographically asymmetric. The results of the FT-IR, ¹H, ¹³C, ¹⁵N NMR and CPMAS study of the crystals are in agreement with the X-ray data. Instead of a continuous absorption, only a broad band is found indicating relatively low proton polarizability in the two types of the cooperative relatively short intramolecular hydrogen bonds. The ¹⁵N NMR chemical shift indicates the protonation of the Schiff base.     

Magnetic susceptibility of 1,1′,2,2′-tetramethylcobaltocene and 1,1′-diethylcobaltocene: Evidence for the dynamic Jahn-Teller effect

The magnetic susceptibility of 1,1′,2,2′-tetramethylcobaltocene, Co[C₅H₃(CH₃)₂]₂, and 1,1′-diethylcobaltocene, Co(C₅H₄C₂H₅)₂, has been studied between 0.99 and 296 K. The data are well reproduced by a calculation of the dynamic Jahn-Teller effect for the ²E_1g(a_1g²e_2g⁴e_1g) ground state of D_5d symmetry. A suitable set of parameter values is given by ζ = 100 cm⁻¹, δ = 150 cm⁻¹, k_JT = 0.40, κ = 0.70. The magnetism of cobaltocene, Co(C₅H₅)₂, may be described by parameter values of comparable magnitude. The results imply a significantly larger reduction of the spin-orbit coupling parameter ζ due to covalency than of the orbital reduction factor κ.     

Conformational and structural analysis of N-N′-bis(4-methoxybenzylidene)ethylenediamine

The Schiff base compound, N-N′-bis(4-methoxybenzylidene)ethylenediamine (C₁₈H₂₀N₂O₂) has been synthesized and its crystal structure has been investigated by X-ray analysis and PM3 method. The compound crystallizes in monoclinic space group P2₁/n with a=10.190(1), b=7.954(1), c=10.636(1) Å, β=111.68(1)°, V=801.1(1) ų, Z=2 and D_cal=1.229 Mgm⁻³. The title structure was solved by direct methods and refined to R=0.056 for 2414 reflections [I>3.0σ(I)] by full-matrix anisotropic least-squares methods. The energy profile of the compound was calculated by PM3 method as a function of θ[N1′–C9′–C9–N1]. The most stable molecular structure of the title compound is the anti conformation, which is different in energy by 5.0 and 1.0 kcal mol⁻¹ from the eclipsed conformation I and gauche conformations, (III and V), respectively.     

Studies directed toward synthesis of guanosine 8,5''-imino cyclonucleosides and derivatives—I

8,5'-Aminimino bridging in the guanosine series using 5'-O-tosyl (1) and 5'-O-mesyl derivatives (2) of 2',3'-O-isopropylidene-8-bromoguanosine (5) and hydrazine gave N³,5'-cyclized product 3 and the N⁵,5'-cyclonucleoside of 4-carboxyhydrazido-5-amino-2-bromoimidazole 4. To exclude the N³,5'-cyclization through ionization in the base moiety, a N²-dimethylaminomethylidene-N¹-methoxymethylene derivative 7 was synthesized from 5 through the N²-protected compound 6. 7 was converted into the N²-dimethylaminomethy analogue 8, which with hydrazine yielded first the N²-deprotected form of 8 (9). 8 or 9 with hydrazine under forcing conditions gave an 8,5'-aminimino-N¹-methox derivative 10. Oxidation of 10 with sodium metaperiodate or sodium nitrite yielded 8,5'-imino-N¹-methoxymethyleneguanosine (11a) and 8,5'-imino-N¹-methoxymethylenexanthosine derivative 11b, respectively. 11a was deprotected to 8,5'-imino-N¹-methoxymethyleneguanosine 12.     

Synthetic analogues of wedelolactone

The syntheses of 7′-methoxy- and 5′,7′,6-trimethoxy-coumarino(3′,4′:3,2)coumarones (IIa and IIb) are described.     

Dynamic behaviour and X-ray analysis of chiral η-allylpalladium complexes. II

The DANTE technique and NOESY two-dimensional method have been employed to observe the isomerization of the chiral cationic complex [Pd(η³-CH₂CMeCH₂(P-P′)]⁺ (1a), where P-P′ = the chiral chelating ligand (S)(N-diphenylphosphino)(2-diphenylphosphinoxymethyl)pyrrolidine. The rate constant was found to be 0.5 s⁻¹ in CHCl₃ at 295 K and 1.50 s⁻¹ in the presence of added free ligand. In the latter case the epimerization proceeds by a π-σ-π mechanism via the intermediacy of a primary η¹-allylpalladium complex. Although the intermediate was not detected, the NMR findings reveal that it has the allylic terminus η¹-bonded to palladium. The structure of 1a in its PF₆⁻ salt has been determined. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ with a 10.029(4) b 19.203(8) c 36.115(6) Å, Z = 8, R = 0.0572 and R_w = 0.0712 for 3716 observed reflections with I > 3σ(I).     

Reaktion eines titanocen—Alkin-Komplexes mit trialkylammoniumtetraphenylborat—eine neue darstellungsweise und erste kristallstrukturanalyse von neutralligandhaltigen kationischen titanocen(III-komplexen [{Cp2Ti(L)2}{BPh4}]

The catioanic d¹-titanocene complexes [{Cp₂Ti(L)₂⁺}{BPh₄⁻}] with L = THF (1) and pyridine (2) were very simply prepared by the reaction of [Cp₂Ti(Me₃SiCCSiMe₃)] with trimethylammoniumtetraphenylborate via a le⁻-oxidation of the 14e⁻-Cp₂Ti-unit to the paramagnetic titanium(III) complex under evolution of molecular hydrogen and the alkyne. Complex 2 is the first example of such a cationic-only neutral-ligand containing complexes without anionic ligands that has been characterized by an X-ray structure analysis.     

[NHN] and [OHO] hydrogen bonding in the adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 1,8-dihydroxy-2,4-dinitronaphthalene (DHDNN)

X-Ray diffraction, IR and ¹H NMR studies were performed on the 1:1 adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 1,8-dihydroxy-2,4-dinitronaphthalene (DHDNN). The adduct crystallizes in the triclinic system, space group , a = 9.911(2) Å, b = 11.212(2) Å, c = 11.194(2) Å, = 68.95(2)°, β = 79.72(2)°, γ = 73.78(2)°, Z = 2. Both [NHN]⁺ and [OHO]⁻ hydrogen bonds formed in the ion pairs are asymmetrical with lengths equal to 2.574(2) Å and 2.466(4) Å respectively. The [NHN]⁺ bridge shows a typical behaviour in the IR spectrum, i.e. a low-frequency absorption between 300 and 700 cm⁻¹. The coupling of [OHO]⁻ hydrogen bonds with the naphthalene π-electron system is so strong that no absorption related to the proton stretching vibrations can be detected in the high- and low-frequency regions. The ¹H NMR chemical shifts for the [NHN]⁺ and [OHO]⁻ bridge protons of 18.63 and 15.81 ppm respectively confirm the strong hydrogen bonds.     

Annellation effects in the perylene and coronene series

Naphtho(2′:3′, 2:3)perylene (VIII), dinaphtho(2′:3′, 2:3); (2″:3″, 8:9)perylene (VII), anthraceno(1′:4′, 1:12)perylene(IV), 1:12-benzonaphtho(2″:3″, 2:3)perylene(II), 1:12-benzonaphtho (2″:3″, 4:5)perylene (III) and 1:12-benzodinaphtho(2″:3″, 2:3); (2″“:3″”,8:9)perylene (XV) were synthesized. There are two different annellation effects in passing from 1:12-benzoperylene (I) to II or III resp., the one in naphthocoronene (V) lies in between these two effects. The annellation effect in the perylene series cannot be related to the molecular axes but is easily explained by the strict application of Robinsons aromatic sextet.     

Hydrogenmaleato bridged supramolecular double chains via π–π stacking interactions: syntheses, crystal structures and magnetic properties of ∞[Cu(phen)X(HL)2/2] with X=Cl (1), NO3 (2) and H2L=maleic acid

Two novel hydrogen maleato (HL) bridged Cu(II) complexes _∞¹[Cu(phen)Cl(HL)_2/2] 1 and _∞¹[Cu(phen)(NO₃)(HL)_2/2] 2 were obtained from reactions of 1,10-phenanthroline, maleic acid with CuCl₂·2H₂O and Cu(NO₃)₂·3H₂O, respectively, in CH₃OH/H₂O (1:1 v/v) at pH=2.0 and the crystal structures were determined by single crystal X-ray diffraction methods. Both complexes crystallize isostructurally in the monoclinic space group P2₁/n with cell dimensions: 1 a=8.639(2) Å, b=15.614(3) Å, c=11.326(2) Å, β=94.67(3)°, Z=4, D_calc=1.720 g/cm³ and 2 a=8.544(1) Å, b=15.517(2) Å, c=12.160(1) Å, β=90.84(8)°, Z=4, D_calc=1.734 g/cm³. In both complexes, the square pyramidally coordinated Cu atoms are bridged by hydrogen maleato ligands into 1D chains with the coordinating phen ligands parallel on one side. Interdigitation of the chelating phen ligands of two neighbouring chains via π–π stacking interactions forms supramolecular double chains, which are then arranged in the crystal structures according to pseudo 1D close packing patterns. Both complexes exhibit similar paramagnetic behavior obeying Curie–Weiss laws χ_m(T−θ)=0.414 cm³ mol⁻¹ K with the Weiss constants θ=−1.45, −1.0 K for 1 and 2, respectively.