Band 23, Heft 12

Das Verhalten von Toluoldämpfen im Plasma einer Glimmentladung bei 10 MHz wird untersucht. Durch Analyse der Produktgemische läßt sich der Reaktionsmechanismus feststellen. Untersuchungen an Benzol, Äthylbenzol und Diphenylalkanen lassen erkennen, welche Produkte in den Toluolansätzen primär und welche durch erneute Anregung der Primärprodukte entstehen. Bei hohen Drucken werden vorwiegend Syntheseprodukte gebildet, wobei die schwächste Bindung im Ausgangsmolekül gelöst wird. Bei niederen Drucken werden auch stärkere Bindungen gelöst. Die Produktzusammensetzung hängt stark von der Frequenz ab. Niedere Frequenzen führen zu intermolekularen Vorgängen (Synthesen), hohe zu intramolekularen (Fragmentierungen).

1-Nitroso-3-nitro-1-methyl-guanidine (NNMG) (at pH 5,5 resp. 6,0) methylates and deaminates the bases of nucleic acids. We treated nucleic bases, nucleosides, nucleoside phosphates and homopolyribonucleic acids with NNMG and we found the following methyl derivates of adenine: 1-methyladenine, 3-methyladenine and N 6 -methyladenine : of guanine: 7-methylguanine and of cytosine: 1-methylcytosine and 3-methylcytosine. Moreover bases of the nucleic acids were deaminated : adenine to hypoxanthine and guanine to xanthine.

Electrical field changes across the function membrane of photosynthesis have been measured via special absorption changes. These occur by the action of the field on pigments which are located within the membrane. - Proton translocation has been measured by absorption changes of added pH indicators. Repetitive flash technique has been used for the sensitive detection of these absorption changes. 1. Each of the two light reactions of photosynthesis sets on one half of the electrical field. 2. The action spectra indicate that the two light reactions which set on the field are identical with those which promote the electron transfer. 3. The voltage set on in the elementary act both light reactions is V 0 =50 mV. 4. Each of the two light reactions translocates one proton across the membrane. 5. The proton uptake is faster than 8 · 10 −3 sec. 6. Two protons are translocated per one electron transferred to a terminal acceptor. 7. A reaction scheme compatible with the measured correlation between the light reactions, electron transfer, field formation, and proton translocation is depicted in Fig. 7.

Cleavage of phorbol-3-ol-12,13,20-triacetate with sodium-periodate proves the presence of an α,β- unsaturated tertiary 1,2-ketol group in phorbol and its location in the five-membered ring. Accordingly 4-O-methyl-phorbol-3-ol-12,13,20-triacetate is not cleaved by sodium periodate, and by zinc/acetic acid phorbol-12,13,20-triacetate is converted to a 4-deoxy-compound.

Oxidation of phorbol with one mole of lead tetraacetate yields bisdehydrophorbol, tiglophorbol and small amounts of phorbolacton-semiacetal. By chemical and spectroscopic investigations of bisdehydrophorbol and its derivatives its complete structure 16 is derived based upon the partial structures and structural elements of phorbol (1 - 3) which have been deduced in preceding communications. By consideration of the mechanism of the oxidative scission of the cyclopropanol unit in phorbol the structure 15 of this new tetracyclic diterpene is obtained. 15 has a pentamethyl-tetradecahydro-1H-cyclopropabenzazulene skeleton (tiglian) carrying as functional groups a tertiary hydroxyl group, an α,β-unsaturated tertiary 1.2-ketol group, a primary allyl alcohol group and a α- [hydroxycyclopropyl] -carbinol group. Phorbol is 4.9.12β.13.20-pentahydroxy-tigliadien- (1.6) -on- (3) (15) , bisdehydrophorbol 4.9.12β.20-tetrahydroxy-13.15-seco-tigliatrien- (1.6.15) -dion- (3.13) (16) the conformations of which have been determined. The structure of phorbolacton-semiacetal is determined in the following communication of this series. Based upon the structure of phorbol and additional chemical and spectroscopic evidence the structure of tiglophorbol (17) is also derived. With the data provided the relative configuration and the conformation of six out of the eight asymmetric centers of phorbol is determined.

Die ausschließliche Charakterisierung von Neuraminsäure mittels der Perjodat-Thiobarbitursäure-Reaktion ist nicht ausreichend. Diese Reaktion erfaßt alle Verbindungen vom Typ der 2-Keto-3-desoxyaldonsäuren. Die aus Sojabohnen und Bananen isolierten Substanzen gehören zur Gruppe dieser stickstofffreien 2-Keto-3-desoxyaldonsäuren. Sie zeigen eine positive Perjodat-Thiobarbitursäure-Reaktion. reagieren aber nicht mit Bials Reagenz.