Oxazolochlorins. 14.

The structure of 8‐oxo‐5,10,15,20‐tetraphenyl‐7‐oxaporphyrin N²⁴‐oxide, C₄₃H₂₈N₄O₃, (4B), shows that N‐oxidation of the pyrrole opposite the oxazolidone group cants the pyrrole out of the mean plane of the chromophore. This also affects the oxazolidone group, which is also slightly canted out. This conformation is qualitatively similar to that of the parent meso‐tetraphenylporphyrin N‐oxide, but dissimilar to that of the porpholactone N‐oxide isomer 8‐oxo‐5,10,15,20‐tetraphenyl‐7‐oxaporphyrin N²²‐oxide, (4A), carrying the N‐oxide at the oxazolidone group. While the degree of canting of the N‐oxidized groups in both cases is comparable (and more pronounced than in the porphyrin N‐oxide case), in (4A) the pyrrolic groups adjacent to the N‐oxidized group are more affected than the opposing group. These differences in the conformational modes may contribute to rationalizing the distinctly different electronic properties of (4A) and (4B).     

E.S.R. and D.S.C. investigations of phase transitions in polymorphic 4-n-alkoxybenzylidene-4′-n-alkylanilines

Abstract

It is shown that the McMillan parameter M = T _SAN/T _N1 (where T _SAN and T _NI are respectively the temperatures of the smectic A to nematic (SAN) and the nematic to isotropic (NI) phase transitions) is useful in analysing the crossover between second and first order behaviour of the S_NN transition in the nO.m homologous liquid crystal series (the 4-n-alkoxybenzylidene-4′-n-alkylanilines). Using a phase diagram of orientational ordering versus M for this series, as obtained in this work (from E.S.R. and D.S.C), a symmetric tricritical point with mean field exponent β₂ = 1 is demonstrated. In a preliminary study of E.S.R. linewidth parameters B and C of nitroxide spin probes dissolved in members of the nO.m series exhibiting a first order S_AN transition, critical-type divergences are observed near this transition. In the case where M is closer to 0.959 (the value at the tricritical point), these divergences appear similar to those previously observed in related nO.m members with a second order S_AN transition; however, they are considerably enhanced for an M value closer to unity (i.e. more removed from the tricritical point). This indicates the importance of coupling between orientational and positional order parameters in the observed critical-type divergences.     

Polysulfonylamines. CXXXII.

The crystal structure of the title compound, C₅H₇N₂⁺·C₁₂H₁₀NO₄S₂⁻, consists of two independent cation–anion pairs, A and B. Within each pair, the H—N—C—N*—H grouping (N*—H is the pyridinium function) and one N—S—O moiety of the anion are linked by N*—H⃛N and N—H⃛O hydrogen bonds to form an antidromic ring motif of type R²₂(8). The remaining amino donors give rise to N—H⃛O hydrogen bonds, connecting the ion pairs into A–B–A–B– chains. The structure testifies to the persistence of the R²₂(8) motif in question, which was previously detected as a highly robust supramolecular synthon in a series of onium di(methane­sulfonyl)­amidates. The structure is pseudosymmetric; the anion positions correspond to space group P2₁/n, but those of the cations do not.     

Acetylenchemie. 9. Mitt. Anellierte imidazole aus N-propinylamid-vorstufen

The Compound 2-(N-Formyl-N-prop-2′-inyl)aminopyridine was cyclised in boiling formic acid to 3-methylimidazo[1,2-a]pyridine, with 3-methylene-2H-imidazo[1,2-a]pyridine as the intermediate. Under similar conditions the 1,3-diprop-2-inylpyrimido[4,5-b]quinoline-2,4-dione resulted from 1-methylimidazo[1,2-a]quinoline-4-carbonic acid-N-2-prop-2′-inylamide and from the 1-prop-2′-inylbenzo[b][1,8]naphthyridin-2-one the 1-methylbenzo[b]imidazo[1,2,3-ij]naphthyridine-4,7-dione as a new ring system, was obtained.     

P.M.R. analysis of several phosphorylated aziridines

Several new phosphorylated aziridines of related structure were prepared. P.m.r. analysis via decoupling experiments provided cis H-H, trans H-H, gem H-H and PNCH coupling values. Similar to simple aziridines, the cis H-H coupling is larger than trans H-H coupling (on vicinal ring carbons) which in turn is larger than gem H-H coupling. In one example operating at 100 MHz and 0° it was possible to detect the presence of two invertomers.     

Hetero-Cope-Umlagerungen. 4. Mitteilung. Regiokontrollierte Indolsynthesen

Hetero-Cope-Rearrangements, Regio-Controlled Synthesis of Indoles The reaction of O-deprotonated N-phenylhydroxylamines 1 with various electron-deficient allenes 2 , 14 , 16 gives, via Michael addition and Cope-rearrangement, substituted anilines 5 , which are easily convertible into indoles 6 . In this manner, sulfoxides 17 , serve as equivalents of 2-vinylindoles. Diels-Alder reaction with this 2-vinylindole equivalent followed by indolisation affords isoquinuclidine derivative 21 which may be a useful precursor for the preparation of Iboga alkaloids.     

Azole. 45.

The three title compounds, namely (Z)‐1‐(4,5‐di­nitro­imidazol‐1‐yl)‐3‐morpholinopropan‐2‐one 2,4‐di­nitro­phenyl­hydrazone, C₁₆H₁₇N₉O₉, (IV), (Z)‐3‐morpholino‐1‐(4‐morpholino‐5‐nitro­imidazol‐1‐yl)propan‐2‐one 2,4‐di­nitro­phenyl­hydrazone, C₂₀H₂₅N₉O₈, (Va), and (E)‐3‐morpholino‐1‐(4‐morpholino‐5‐nitro­imidazol‐1‐yl)propan‐2‐one 2,4‐di­nitro­phenylhydra­zone tetra­hydro­furan solvate, C₂₀H₂₅N₉O₈·C₄H₈O, (Vb), have been prepared and their structures determined. In (IV), the C‐4 nitro group is nearly perpendicular to the imidazole ring and the C‐4—NO₂ bond length is comparable to the value for a normal single Csp²—NO₂ bond. In (IV), (Va) and (Vb), the C‐­5 nitro group deviates insignificantly from the imidazole plane and the C‐5—NO₂ bond length is far shorter in all three compounds than C‐4—NO₂ in (IV). In consequence, the C‐4 nitro group in (IV) is easily replaced by morpholine, while the C‐5 nitro group in (IV), (Va) and (Vb) shows an extraordinary stability on treatment with the amine. The E configuration in (Vb) is stabilized by a three‐centre hydrogen bond.     

Die sterischen Bedingungen der Fragmentierungsreaktion. II. Teil. Stereoisomere 3-Aminocyclohexyl-p-toluolsulfonate. Fragmentierungsreaktionen, 15. Mitteilung

The solvolytic fragmentation of cis- and of trans-3-amino-cyclohexyl p-toluenesulfonates 8a and 9a and the corresponding N, N-dimethyl derivatives 8b and 9b has been studied. In 80% ethanol the cis-amino-tosylates 8a and 8b react faster than the homomorphous cis-3-alkyl-cyclohexyl tosylates 11a and 11b to yield fragmentation product exclusively or predominantly. The synchronous mechanism predictable on stereoelectronic grounds is therefore indicated.     

Reactivity and gelation. I. Intrinsic reactivity

The method of Case is used with the Flory-Stockmayer gelation criterion to derive a critical transition equation for polycondensation of multifunctional reactants bearing coreactive functional groups of two species A and B, where the B groups may be of unequal intrinsic reactivity. Systems of the types R(A)₂/R′(B)₄ and R(A)₂/R′(B)₄/R′′(B)₂ are considered with the B groups divided into two classes characterized by a reactivity ratio in the range 0.1 to 10. If the reactivities are sufficiently different the polymerization can be regarded as a multistage process. Intramolecular reactions are not considered.     

Prins-Reaktionen mit Arylaldehyden, 3. Mitt.

By reaction of excess benzaldehyde with cyclohexene in presence of sulfuric acid besider-2,c-4-diphenyl-(t-4aH,c-8aH)-hexahydro-4H-1,3-benzodioxin (2) andr-4-phenyl-(t-4aH,c-8aH)-hexahydro-4H-1,3,2-benzodioxathiin-2,2-dioxide (3),trans-2-benzyloxycyclohexyl phenyl ketone (5) and (E)-3-benzylidene-1-cyclohexenyl phenyl ketone (6) are obtained. The formation of5 and6 is shown to proceed via an acid catalyzedCannizzaro reaction of benzaldehyde.

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2. Mitt.:H. Griengl undK. P. Geppert, Mh. Chem.107, 675 (1976).     

Photochemische reaktionen. 108. Mitteilung. Photochemistry of N-acylazoles. VI. Photoreactivities of 1-acyl-1,2,4-triazoles and of 2-acyltetrazoles

Contrary to the findings in the photolysis of N-acylimidazoles [2] irradiation of 1-acyl-1,2,4-triazoles afforded no photo-Fries product, but instead products formed via the corresponding acyl radicals and aldehydes. Photolysis of 2-acyltetrazoles gave in part the same products as those obtained from the irradiation of the corresponding acyl-triazoles as well as 2-alkyl-1,3,4-oxadiazoles. N-Acyltetrazoles didn't give any photo-Fries product neither.     

Pteridines. Part CXIX.

A variety of pyrimidine precursors 12 – 25 were converted into a series of new 7‐hydroxylumazines (=7‐hydroxypteridine‐2,4(1H,3H)‐diones) 26 – 35 which functioned as starting materials for the transformation into the corresponding 7‐chlorolumazines 36 – 45 . Subsequent reaction with hydrazine led to the 7‐hydrazinolumazines 46 – 55 which gave on nitrosation the 7‐azidolumazines 1 and 56 – 64 . These compounds were subjected to short heating in xylene whereby 1 and 56 – 61 showed a new pteridine–purine interconversion in forming a new type of 1,3‐disubstituted or 3‐substituted xanthin‐8‐amine‐derived nitrilium ylides (2,3,6,7‐tetrahydro‐N‐methylidyne‐2,6‐dioxo‐1H‐purin‐8‐aminium ylides) 11 and 65 – 70 . The presence of an additional 6‐alkyl substituent in the 7‐azidolumazines 63 and 64 or of an unsubstituted N(3) position in 62 caused further rearrangement to xanthine‐9‐carbonitriles 71 – 73 . Prolonged heating of 7‐azido‐1,3‐dimethyllumazine ( 1 ) also afforded theophylline‐9‐carbonitrile (=1,2,3,6‐tetrahydro‐1,3‐dimethyl‐2,6‐dioxo‐9H‐purine‐9‐carbonitrile; 5 ). The nitrilium ylide function was established by NMR and UV spectra as well as by elemental analyses. Confirmation of the nitrilium ylide structures was suggested by the result of the heating of 1,3‐dimethyl‐N‐methylidynexanthin‐8‐aminium ylide 11 in EtOH or of 1 in pentan‐1‐ol leading to 8‐aminotheophylline (=8‐amino‐3,7‐dihydro‐1,3‐dimethyl‐1H‐purin‐2,6‐dione; 74 ).     

13C n.m.r. spectra of some thiobenzamides. Correlation between 13C and 1H n.m.r. spectra and signal assignments of syn and anti CH2 groups

¹³C n.m.r. spectra of a series of N,N-disubstituted thioamides have been recorded and signal assignments were performed. Separate signals are observed for methylene groups fixed on the nitrogen atom. Since the carbon atom syn to the thiocarbonyl sulfur resonates at higher field than the anti carbon, the syn-anti assignment in ¹H n.m.r. is easily obtained by selective double irradiation. This method, which is rapid and reliable, affords a rather general solution to the interesting problem of resonance assignments in tertiary amides and thioamides (and in analogous molecules such as oximes and nitrosamines).     

Triaziridine. 9. Mitteilung. Ringöffnungen von Triaziridinen

Triaziridines. Ring Openings of Triaziridines Eleven triaziridine derivatives were heated at 60° in CDCl₃ to obtain information on the tendency towards, resp. the resistance to, ring opening of the N₃-homocycle by thermolysis. Among these triaziridines, there are three which contain, as one of the substituents, a methoxycarbonyl group (ester derivatives 1 , 5 and 16 ), three a methyl group (methyl derivatives 18 , 24 , and 26 ), three an H-atom ( 14 , 27 , and 30 ), and two a negative charge ( 31 and 32 ). The other two substituents in each of these four classes of triaziridines are trans-located i-Pr groups ( 1 , 18 , 27 , and 31 ), cis-located i-Pr groups ( 5 , 24 , 14 , and 32 ), and a 1,3-cis-cyclopentylidene group ( 16 , 26 , and 30 ). As major products these mild thermolyses, we isolated : from the trans-ester 1 and from the annellated ester derivative 16 , the 1-acyl-azimines 2 and 17 , respectively, from the cis-ester 5 , the 3-acyl-triazene 4 , from the trans-methyl derivative 18 , the (E)-diazene 19 , and hexamine 21 , from the cis-methyl derivative 24 the 2-methylazimine 25 , both from the trans- and cis-H-derivatives 27 , and 14 , respectively, the H- triazene 13 and, finally, both from the trans-and cis-anion 31 and 32 , respectively – after protonation the H-triazene 13 and – after methylation – the methyl-triazene 33 . The same thermolysis of the annellated methyl and H-derivatives 26 and 30 , respestively, resulted only in decomposition. These results can be uniformly interpreted with a primary opening of the triaziridine ring by rupture of one of the two types of N? N bonds lending to azimines or triazenide anions. Some of the azimines were isolable, namely 2 , 17 , and 25 , and one was spectroscopically observable as an intermediate, namely 11 on the way to the triazene 4 . The other azimines are plausible intermediates to the isolated products, namely 15 on the way to 13 , and 22 on the way to 19 and 21 . The triazenide anion 28 is the evident intermediate on the way to 13 or to 33 . The annellated azimines are assumed not be formed from 26 and 30 , or then to be be decomposed under the conditions of their formation. We conclude that the triaziridine derivatives 1, 16 , and 18 underwent thermal ring opening between N(1) and N(2), while the derivatives 5 , 14 , 24 , 27 , 31 , and 32 were ruptured between N(2) and N(3); no conclusion was possible on the ring opening of the derivatives 26 and 30 . The predominant formation of the (Z)-azimine 2 from the trans-triaziridine 1 , and of the (E)-isomer 3 – among the two azimines – from the cis-triaziridine 5 suggests a stereospecificity in the triaziridine ring openings. This would, however, not be expected to be observable in the products from the other triaziridines, since both N? N bonds of the azimine 25 and of the anion 28 probably rotate rapidly and since the secondary trans formations of the other primary products are not able to retain configurational information.     

Intramolecular diels-alder reactions. 4. Additions to naphthalene

N-Methyl-N-2-propynyl-1-naphthalenecarboxamide, N-methyl-N-2-propynyl-1-naphthaleneacetamide, and N-methyl-N-3-butynyl-1-naphthalenecarboxamide undergo intramolecular Diels-Alder reactions at 190°, 250°, and 270° to give lactams 1,6 , and 9 , respectively. The cyclization temperatures are higher by 80-120° as compared to those of the corresponding anthracene derivatives. Elaboration of lactam 6 gave the trans-4a-aryldecahydroisoquinoline derivative 7a which, as the (-) isomer, was shown to have the same absolute stereochemistry as morphine.     

Über Pterinchemie. 56. Mitteilung. Die Kristallstruktur von Xanthopterin-hydrochlorid

The crystal structure of xanthopterine-hydrochloride. The crystal structure of the title compound, a pterine, has been determined by X-ray analysis (direct methods) and refined with 1332 structure amplitudes to R = 0.027. The crystal system is monoclinic, space group P2_1/c, with unit cell dimensions a = 7.942, b = 8.417, c = 12.076 Å, β = 93.77°. The molecule is protonated at the N(1)-position. The angle between the planes of the pyrimidine and pyrazine rings is 2.02°.     

Zur Chemie der Pyrrolpigmente, 63. Mitt.

Using hexamethylphosphoric acid triamide (HMPT) as solvent for bilatrienesabc and mainly for 2,3-dihydrobilatrienes-abc (which serve as the most suitable models for the biliproteid chromophores) a small hypsochromic shift and a dramatic change of the relative intensities of short and long wavelength absorption bands, as compared to solutions in CCl₄, is observed. Applying NMR-spectroscopic techniques (¹⁵N-,¹³C-,¹H-) a predominance of the (4Z,9E,15Z) diastereomer forming a 5syn-, 10anti-, 14syn-periplanar orclinal conformation is deduced. The stabilisation of this configuration and conformation arises from strong hydrogen bonds between the acidic protons of the bilins andHMPT. Interactions of this kind seem to be the main source of energy to stretch the otherwise coiled bilin chromophore of (4Z,9Z,15Z)-5sp,10sp,14sp geometry. Stretched systems of the type bilin-HMPT may serve as a valuable model for the natural biliproteides.

Herrn Prof. Dr.A. Eschenmoser zum 60. Geburtstag gewidmet.116, 1065 (1985).     

Triterpene glycosides from Astragalus and their genins. LXXVIII. Chemical transformation of cycloartanes. VI. Partial synthesis of cycloadsurgenina

Cycloadsurgenin, 20R,24 S-epoxycycloartan-6α,25-diol-3,16-dione, was partially synthesized in four steps from cyclosieversigenin. Side products with the structures 17E,24S-cycloart-17-en-6α,24,25-triol-3,16-dione and 17Z,24 S-cycloart-17-en-6α,24,25-triol-3,16-dione were obtained in addition to the desired product. Presented at the 1st International Symposim on Edible Plant Resources and the Bioactive Ingredients, Xinjiang, China, July 25–27, 2008. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 591–595, November–December, 2008.     

Glyconothio-O-lactones. Part I. Preparation and reactions with nucleophiles

Furanoid and pyranoid glyconothio-O-lactones were prepared by photolysis of S-phenacyl thioglycosides or by thermolysis of S-glycosyl thiosulfinates, which gave better results than the thionation of glyconolactones with Lawesson's reagent. Thermolysis of the thiosulfinates obtained from the dimannofuranosyl disulfide 7 or the manofuranosyl methly disulfide 8 (Scheme 2) gave low yields of the thio-O-lactone 2 . However, photolysis of the S-phenacyl thioglycoside 6 obtained by in situ alkylation of the thiolato anion derived from 5 led in 78–89% to 2 . Similarly, the dithiocarbonate 10 was transformed, via 11a , into the ribo-thio-O-lactone 12 (79%). Thermolysis of the peracetylated thiosulfinates 14 (Scheme 3) led to the intermediate thio-O-lactone 15 , which underwent facile β-elimination of AcOH (→ 16 , 75%) during chromatography. The perbenzylated S-glucopyranosyl dithiocarbonate 18 (Scheme 4) was transformed either into the S-phenacyl thioglucoside 19 or into a mixture of the anomeric methyl disulfides 21a/b . Whereas the photolysis of 19 led in moderate yield to 2-deoxy-thio-O-lactone 20 , oxidation of 21b and thermolysis of resulting thiosulfinates gave the thio-O-lactone 4 (79%), which was transformed into 20 (36%) upon photolysis. The pyranoid manno-thio-O-lactone 26 was prepared in the same way and in good yields from 22 via the dithiocarbonate 24b and the disulfide 25 . The ring conformations of the δ-thio-O-lactones, flattened ⁴C₁ for 15 and 4 and B_2,5 for 26 , are similar to the ones of the O-analogous oxo-glyconolactones. The reaction of 2 (Scheme 5) with MeLi and then with MeI gave the thioglycoside 27 (29%) and the dimeric thio-O-lactone 29 (47%). The analogous treatment of 2 with lithium dimethylcuprate (LiCuMe₂) and MeI led to a 4:1 mixture (47%) of 31 and 27 . The structure of 2 was proven by an X-ray analysis, and the configuration at C(6) and C(5) of 29 was deduced from NOE experiments. Substitution of MeI by CD₃I led to the CD₃S analogues of 27 , 29 , and 31 , i.e. 28 , 30 , and 32 , respectively, evidencing carbophilic addition and ‘exo’-attack on 2 by MeLi and the enethiolato anion derived from 2 . The preferred ‘endo’-attack of LiCuMe₂ is rationalized by postulating a single-electron transfer and a diastereoselective pyramidalization of the intermediate radical anion.     

Structural characterisation of a water-soluble polysaccharide from tissue-cultured Dendrobium huoshanense C.Z. Tang et S.J. Cheng

A water-soluble polysaccharide TC-DHPA4 with a molecular weight of 8.0 × 10⁵ Da was isolated from tissue-cultured Dendrobium huoshanense by anion exchange and gel permeation chromatography. Monosaccharide analysis revealed that the homogeneous polysaccharide was made up of rhamnose, arabinose, mannose, glucose, galactose and glucuronic acid with a molar ratio of 1.28:1:1.67:4.71:10.43:1.42. The sugar residue sequence analysis based on the GC-MS files and NMR spectra indicated that the backbone of TC-DHPA4 consisted of the repeated units:→6)-β-Galp-(1→6)-β-Galp-(1→4)-β-GlcpA-(1→6)-β-Glcp-(1→6)-β-Glcp-(→. The sugar residue sequences β-Glcp-(1→)-α-Rhap-(1→3)-β-Galp-(1→, β-Glcp-(1→4)-α-Rhap-(1→3)-β-Galp-(1→, β-Galp-(1→6)-β-Manp-(1→3)-β-Galp-(1→, and α-l-Araf-(1→2)-β-Manp-(1→3)-β-Galp-(1→ were identified as the branches attached to the C-3 position of (1→6)-linked galactose in the backbone.