Alstonia scholaris: Struktur des Indolalkaloides Narelin

Alstonia scholaris: The structure of the indole alkaloid nareline Besides the known akuammidine, picralinal, picrinine and pseudoakuammigine a new indole alkaloid called nareline (M=352) was isolated from Alstonia scholaris R. BR. , which belongs to the plant family of Apocynaceae. Its structure 2 was deduced by single crystal X-ray diffraction. 2 represents the absolute configuration. The spectroscopic data of 2 and its derivatives (Scheme 1) as well as their chemical behavior support this structure. In biogenetic sense nareline is related to the bases akuammiline ( 4 ) and picraline ( 5 ) (Scheme 2). In contrast to those the C-atom 5 is exocyclic and represents an aldehyde group which forms together with the oxygen atom of the N (4)-hydroxylamine group a cyclic half acetale. - By oxidation (CrO₃/CH₃COOH) of 2 the oxindol derivative 19 (oxonareline) is formed which contains a cyclic acetal as a partial structure element (Scheme 4).     

Critical parameters and optimization of a magnesium-selective liquid membrane electrode for application to human blood serum

Summary The selectivity of a new magnesium ionophore (ETH 7025) induced in membranes of different compositions is experimentally studied in view of the ion activities in human serum. The required selectivity coefficient against calcium for the application of an ion-selective magnesium electrode to human serum is calculated for the worst case. Other critical parameters for the application of a liquid PVC-based ion-selective membrane to undiluted human serum discussed are: the sensor lifetime which is related to the lipophilicity of the carrier as well as the ruggedness of the membrane against interactions with components of the relatively lipophilic sample.     

Säurekatalysierte Umlagerung von Allyl-cyclohexadienon-tosyl-hydrazonen: Beispiel einer Dienimin-Anilin-Umlagerung

The tosylhydrazones of 4-allyl- and 4-crotyl-4-methyl-cyclohexa-2, 5-dien-l-one ( 14 and 15 ) rearrange in the presence of acid to yield the corresponding 2-allyl- and 2-α-methylallyl-hydrazines 17 and 18 , respectively. A similar behaviour is shown by the tosylhydrazone of 2-allyl-2-methyl-cyclohexa-3, 5-dien-1-one ( 16 ). 16 could not be isolated. The observed acidcatalysed [3 s, 3 s]-sigmatropic rearrangement of the tosylhydrazones can be regarded as a rearrangement of the dienimine-aniline type.     

Determination of the diastereomers of vitamin K1

A method is described for the gas-chromatographic determination of the diastereomers of vitamin K₁ (phylloquinone) in the form of their dihydro dimethyl ethers. The reported method of derivatization and chromatographic analysis in conjunction with optical rotation measurements are useful approaches for characterization of vitamin K₁ samples with respect to their origin.     

Kinetik und Mechanismus der Diazotierung, 18. Mitt.: Kinetik und Mechanismus der Diazotierung des Anilins in chlorwasserstoffsaurem Methanol

Ohne ZusammenfassungI.H. Schmid undG. Muhr, Ber. dtsch. chem. Ges.70, 421 (1937); II.H. Schmid, Z. Elektrochem.43, 626 (1937); III.H. Schmid, Atti X. Congr. internat. Chim. Roma2, 484 (1938); IV.H. Schmid undA. Woppmann, Mh. Chem.83, 346 (1952); V. und VI.H. Schmid undR. Pfeifer, Mh. Chem.84, 829, 842 (1953); VII.H. Schmid, Mh. Chem.85, 424 (1954); zusammenfassender Ber.:H. Schmid, Chemiker-Ztg.78, 565, 683 (1954); VIII.H. Schmid, Mh. Chem.86, 668 (1955); IX.H. Schmid undA. F. Sami, Mh. Chem.86, 904 (1955); X.H. Schmid undE. Hallaba, Mh. Chem.87, 560 (1956); XI.H. Schmid undA. Woppmann, Mh. Chem.88, 411 (1957);H. Schmid, Mh. Chem.88, 161, 344 (1957); XII.H. Schmid undM. G. Fouad, Mh. Chem.88, 631 (1957);H. Schmid, Österr. Pat. 191 399, Kl. 12e₂ (Juni 1957);H. Schmid, Chemiker-Ztg.81, 603 (1957); XIII. und XIV.H. Schmid undCh. Essler, Mh. Chem.88, 1110 (1957);90, 222 (1959); XV.H. Schmid undA. Woppmann, Mh. Chem.90, 903 (1959); XVI.H. Schmid undCh. Essler, Mh. Chem.91, 484 (1960); XVII.H. Schmid undG. Muhr, Mh. Chem.91, 1198 (1960);H. Schmid, Mh. Chem.92, 174 (1961).     

Zur Photochemie von Allylaryläthern. 55. Mitteilung über Photoreaktionen

The photochemical reactions of different allyl aryl ethers (Scheme 3) were investigated in hydrocarbons (Chap. 3.1) and in alcoholic solvents (Chap. 3.2). The composition of the photoproducts depended very much on the nature of the solvent. Irradiation (3–95 h) of different methyl substituted allyl aryl ethers ( 1, 3, 5, 7 and 11 ) with a low pressure mercury lamp (λ_Emiss. = 254 nm; 6 or 15 Watt) under argon (quartz vessel) resulted in the formation of 2-, 3– and 4-substituted phenols, dienones and products of consecutive reactions (Tables 1–4 and 6). The results suggested that all products were formed by homolytic cleavage of the C? O bond in the singlet state of the ethers to intermediate radical-geminates (Scheme 5) followed by radical recombination of the two fragments. No products were formed by concerted processes (Table 5, Schemes 5 and 6). Upon irradiation of allyl aryl ethers lacking alkyl substituents at position 4 ( 1 and 5 ) in protic solvents, mainly 2- and 4-allylated phenols were obtained (Tables 1 and 4); 3-allylated phenols were formed only in small amounts (0.02%). However, in aromatic hydrocarbons or cyclohexane 3-allylated phenols were obtained from 1 , 5 and 11 in significant amounts (3–11%; Tables 1, 4 and 6). E.g., upon irradiation of allyl-2,6-dimethyl-2,4-cyclohexadien-1-one ( 6 ) besides 3- and 4-allyl-2, 6-dimethyl-phenol ( 23 and 24 ). Irradiation of 5 in methanol afforded 23 and 6 only in traces, whereas 24 was the main product.     

Self-Assembly of Gold Nanoclusters on Molecularly Modified GaAs

The elaboration of closed-packed monolayers of Au₅₅(PPh₃)₁₂Cl₆ clusters on oxidized and non-oxidized GaAs surfaces is reported. The first part of this work describes the use of silanethiol modified GaAs oxide surfaces to trap 18 nm gold colloids and Au₅₅(PPh₃)₁₂Cl₆ clusters. The surfaces characterized by AFM measurements present high-quality coverage on a quite long range for both metallic species. The second part is devoted to the elaboration of Au₅₅(PPh₃)₁₂Cl₆ cluster monolayers on non-oxidized p-type GaAs substrates, functionalized with dithiol molecules. AFM measurements demonstrate the presence of closed-packed two-dimensional arrangements of Au₅₅ clusters.     

Photochemisches Verhalten von 1- und 2-alkylierten 1, 2-Dihydronaphthalinen bei tiefen Temperaturen

The irradiations of 1, 1-dimethyl- (8), 1, 1-di-(tri-deuteriomethyl)- (d₆– 8 ), 1, 1, 2, 2-tetramethyl- ( 9 ) and cis- and trans-1, 2-dimethyl-1, 2-dihydronaphthalenes (cis- and trans- 10 ) were investigated in 2, 2-dimethylbutane/pentane at ?100° using a mercury high-pressure lamp, and with mercury high- and low-pressure lamps at room temperature. The results were compared with one another, and those of the individual compounds are collected in schemes 2 and 4–7. The most important results are the following: 1. The 1, 2-dihydronaphthalenes undergo a conrotatory ring opening to the o-quinodimethanes on irradiation with high- or low-pressure lamps at room temperature or at ?100°. Thermal reactions ([1, 7a]H-shifts, electrocyclisations) are suppressed at ?100°. The o-quinodimethanes formed from 8 (scheme 2), 9 (scheme 5) or cis- 10 (scheme 6) undergo on irradiation with the high-pressure lamp, [1, 5]H-shifts or photochemical Diels-Alder reactions after renewed photochemical excitation, to yield the benzobicyclo[3.1.0]hex-2-ene derivatives. These Diels-Alder reactions do not proceed stereospecifically, and therefore are not orbital symmetry controlled reactions. 2. If the 1, 2-dihydronaphthalenes are irradiated at room temperature with either a high- or a low-pressure lamp, then the initially formed o-quinodimethanes undergo thermal [1, 7a]H-shifts, in preference to all other reactions, as long as this is sterically possible; the resulting products can undergo secondary photochemical transformations. Such o-quinodimethanes are formed on irradiation of 8, 9 and cis- 10 . From trans- 10 , an o-quinodimethane mixture is formed, of which one component (cis, cis- 22 ) undergoes thermal [1, 7a] H-shifts, while the other (trans, trans- 22 ) suffers a thermal disrotatory electrocyclisation to give cis- 10 . If a high-pressure lamp is used in the last experiment, then the competing photochemical Diels-Alder cyclisation to bicyclic compounds of the type 23 (scheme 7) can result in the trans, trans- 22 . As was shown by Salisbury [3], and confirmed by ourselves in other cases [2], photochemical Diels-Alder reactions or [1, 5]H-shifts in the o-quinodimethanes require light of wavelength ? 400 nm (high-pressure lamp). The present photochemical investigations amplify and confirm our earlier conclusions concerning the photochemistry of the 1, 2-dihydronaphthalenes [2].