Eckehard V. Dehmlow

Anwendungen der phasentransfer-katalyse—4: Halogenaustausch und reaktivitäten bei dibrom-, chlorbrom- und dichlorcarben

Abstract Exchange with external halogenide is possible in phase transfer catalytical generations of dihalocarbenes. CHBrCl2 and CHBr2Cl yield adducts of all three possible combinations, CBr2, CBrCl and CCl2. Consumption of haloform is accelerated by the presence of olefin, the amount of hydrolysis competing with carbene formation, however, is reduced thereby. Contrary to claims in the literature no optical induction is observed in CX2 additions. These results support once more the intermediacy of free CX2. CBr2 is more reactive and electrophilic than CCl2 under phase transfer catalysis conditions, again contrary to literature claims. An example of a differing mode of reaction of chloroform and bromoform is given.

Anwendungen der phasen-transfer-katalyse 1.: eine neue variante der dichlorcarben-erzeugung

ANWENDUNGEN DER PHASEN-TRANSFER-KATALYSE I. : EINE NEUE VARIANTE DER DICHLORCARBEN-ERZEUGUNG Eckehard V. Dehmlow Institut fhr Organische Chemie der Technischen Universitat Berlin D-1000 Berlm 12, Strasse des 17. Juni 135, Germany (Reoeived in Germany 12 November 1975; reeeired in UK for publxmaflon 1 Deeember 1975) Umsetzungen organischer Substanzen m organischen Ltisungsmitteln mit Reagentlen, die m fester Form oder m Wasser gel&t vorliegen, kGnnen durch Phasentransfer-Katalysatoren ermbglmht bzw. stark beschleunigt werden 1) . Derartige Verfahren brmgen gegeniiber konventtonellen Vorschriften h&fig Emsparungen an teuren absoluten oder aprotischen Ltlsungsmitteln, Reaktionsund Aufarbeitungszelt mit sich.

Neue heptaen-makrolide—II : Grundskelett, stellung der funktionellen gruppen und struktur der aglykone☆

Abstract Drastic hydrogenation and reduction of the two antibiotics yielded numerous products each with only a few functional groups. TLC separation, and mass spectroscopic evidence combined with results from chemical reactions 1 led to the structural proposals 1 and 2 , in which only the positions of attachment of mycosamine remain uncertain.

Neue heptaen-makrolide—I : Charakterisierung und abbau

Abstract The antibiotic DJ-400 isolated from streptomyces was separated by counter current distribution into two similar components B1 and B2. Retroaldolizations yielded N-methyl-p-aminoacetophenone and 3,5-heptadienone from B1, and p-aminoacetophenone from B2. With stronger alkali an octaenal was isolated from both components. Both, B1 and B2, contain free β-ketoacid systems and the amino sugar mycosamine. Further experiments have led to partial structures 8 or 9 for the surrounding of the chromophore.