Photochemische Reaktionen. 34. Mitteilung. Die Photoisomerisierung von 3-Oxo-Δ1;4-Steroiden in Dioxanlösung. 3,11-Dioxo-17β-acetoxy-Δ1;4-androstadien und 3-Oxo-17β-acetoxy-Δ1;4;9,11-androstatrien

Ultraviolet irradiation of the steroidal cross-conjugated dienones 3 and 7 , and of the bicyclohexenone derivative 16 in dioxane solution produced the virtually quantitative isomerizations 3 → 11 (Chart 3) and 7 → 16 → 17 (Chart 6). These conversions are consistent with the previously established general scheme a → b → c → d → e (Chart 1). By analogy with these results, it is suggested that the photo-isomers 9 and 10 of O-acetylprednisone ( 8 ) represent products resulting from multiple photorearrangements rather than from direct transformations, as had been proposed in the literature.     

Photochemische Reaktionen. 71. Mitteilung. Die Photoisomerisierung eines spirocyclischen α, β-Epoxyketons

On direct UV. irradiation and on triplet sensitization with acetophenone the spirocyclic epoxyketone (R)-(?)- 9 undergoes racemization (Φ^313/334 0.014, Φ^Sens 0.0060) and rearrangement to the enantiomeric spiro-β-diketones (R)-(+)- 14 (Φ^313/334 0.068, Φ^Sens 0.0037) and (S)-(?)- 14 (Φ^313/334 0.024, Φ^Sens 0.0023). The quantum yield data show that triplet reaction due to intersystem crossing is unimportant on direct irradiation, and they exclude that one common diradical intermediate of type d (Scheme 8) for the three reaction paths is involved in both the singlet and the triplet reaction. The postulate of photolytic Cα? O epoxide cleavage to intermediates of type d for the rearrangement requires that the rate of rearrangement is greater than the rate of rotation around the Cα? Cβ; bond in a given d , and that the rate difference is greater in singlet-generated d than in the triplet analogue. Reclosure of diradicals d and/or photolytic Cα? Cβ cleavage to diradical e and reclosure can account for the racemization of 9 . The optically active spiro-β-diketone 14 was found to racemize also on direct irradiation and on triplet sensitization. Furthermore, both 14 and the isomeric β-diketone 20 , which was obtained by UV. irradiation of the homocyclic epoxyketone 19 , photochemically isomerize to the enol lactones 23 and 21 , respectively.     

Stoffwechselprodukte von Mikroorganismen 227. Mitteilung. Isolierung und Strukturaufklärung von Rutamycin B

Isolation and Structure of Rutamycin B Botrycidin was found to be identical with rutamycin. From the cultures of the actinomycete producing botrycidin and the venturicidines. A and B, a fourth antifungal antibiotic, rutamycin B, was isolated. Through a series of degradation products its structure could be correlated to that of rutamycin, which had been determined before by an X-ray structural analysis. Rutamycin B has been identified as 12-deocy-rutamycin.     

Photochemische Reaktionen. 62. Mitteilung [1]. Die Photofragmentierung von O-acetyljervin

On ultraviolet irradiation O-acetyljervine ( 1 ) is subjected to several parallel fragmentations. From the complex reaction mixtures obtained in a variety of solvents (dioxan, tetrahydrofuran, acetonitrile, iso-octane, benzene) the major alicyclic products 6 – 8 and the heterocyclic compounds 12 – 16 have been isolated. Products 6 – 8 undergo further photochemical changes, e.g., decarbonylation of 7 to 9 and hydrolytic cleavage of 8 to 10 . These photofragmentations are initiated almost specifically upon selective π → π* excitation at 2537 Å with a quantum yield of Φ²⁵³⁷ = 0.145 for conversion of starting material. Reaction upon irradiation in the long-wavelength n → π* absorption band is very much less efficient (Φ³⁶⁶⁰ = 0.611 · 10^?3, both determinations for O-trimethylsilyl-jervine ( 2 ) in tetrahydrofuran). A high degree of photostability is observed also at 2537 Å on N-protonation of O-acetyljervine ( 1 ) in acetic acid. Furthermore, reactivity is greatly reduced for the N-methyl ( 3 ) and N-acetyl ( 4 ) derivatives in neutral solvents at 2537 Å. N-Chloro-O-acetyljervine ( 5 ) in dioxan at 2537 Å gave preferentially O-acetyljervine hydrochloride.     

Photochemische Reaktionen 42. Mitteilung [1]. Photoisomerisierung von α, β-Epoxyketonen II Der sterische Verlauf der Umlagerung von 3-Oxo-4, 5-oxido-Steroiden

The photorearrangement previously described [3] of saturated and Δ¹-unsaturated 3-oxo-4,5-epoxy-10β-steroids to 3,5-dioxo-10(5 →4)-abeo compounds proceeds most likely via a radical 1,2-alkyl shift (Chart 1). The similar rearrangements of the related 10α-epoxyketone 10 and the 4-methyl-epoxyketones 13 , 15 , 16 , 20 and 21 to the corresponding 3,5-diketones occurred without epimerization at the migrating carbon atom (C-10) and the site of substitution (C-4) (Chart 3). The stereochemical control of the rearrangement is in agreement with the earlier proposed mechanism of a concerted alkyl radical shift in these alicyclic systems.     

Stoffwechselprodukte von Mikroorganismen. 202. Mitteilung. Strukturaufklärung von Elaiophylin: Spektroskopische Untersuchungen und Abbau

Structure Elucidation of Elaiophylin: Spectroscopy and Chemical Degradation The structure of the antibiotic elaiophylin (azalomycin B) was elucidated by extended spectroscopic investigations and chemical degradation. Elaiophylin ( 26 ) is a macrodiolide with a 16membered dilactone ring. The synthesis of 7-acetoxy-6-ethyl-3-octanone ( 14 ), the acetyl derivative of an important degradation product, is described.     

Photochemische Reaktionen. 51. Mitteilung [1]. Zur Photochemie von gesättigten β-Ketosulfiden III. Strukturaufklärung eines weiteren Photoproduktes Zusammenfassende Beurteilung des photochemischen Reaktionsbildes

Ultraviolet irradiation of the saturated β-ketosulfide 2 [(charge-transfer)- or (n → π*)-excitation] in methanol or benzene solutions resulted in the formation of the products 4, 5a, 6 (due to α-cleavage) and 7 [due to (C_α–S)-fission]. Compounds 4, 6 and 7 have been described earlier [1] [2]. The structure elucidation of 5a is reported in this paper. The photochemistry of the β-ketosulfide 2 is summarized.     

Stoffwechselprodukte von Mikroorganismen. 216. Mitteilung. Isolierung,Strukturaufklärung und Synthese von Ferrioxamin H

Metabolites of Microorganisms. 216. Isolation, Structure and Synthesis of Ferrioxamine H The structure of ferrioxamine H , a minor component of the sideramine complex of actinomycetes, was determined by spectroscopic investigations, degradation and synthesis. Ferrioxamine H is the Fe (III)-complex of 11,22-dihydroxy-4, 12, 15, 23-tetraoxo-5,11,16,22-tetraazatetracosanoic acid ( 2 ).     

Strukturaufklärung von N6-, 9- und 7-Acyladeninen durch 1H-und 13C-NMR-Spektroskopie von Festkörpern und in Lösung

Structure Determination of N⁶-, 9-and 7-Acyladenines by ¹H- and ¹³C-NMR Spectroscopy of Solids and in Solution . Adenine (1) reacts with carboxylic acid anhydrides or chlorides 2 to yield the acyladenine isomers 3–5 . The isomeric structures were determined by ³³C- and ¹H-NMR spectroscopy in solution and by solid-state ¹³C-NMR spectroscopy.     

Photochemische Reaktionen. 76.Mitteilung [1]. UV.-Bestrahlung von 11-Oxo-Steroiden V Die Photoisomerisierung von 3,20-Diäthylendioxy-5α,14β,17α-pregnan

The UV.-isomerisation of 11-oxo-14β,17α-pregnane 9 to the 11,19-cyclo-derivative 11 is described. In addition the Pb(OAc)₄-fragmentation of photoproduct 11 was investigated. 11 yielded besides the expected 11-oxo-19-hydroxy-pregnane 18 the novel 9,11-seco-11,19-cyclosteroid 19 . The structure of 19 was established by chemical transformations and subsequently confirmed by X-ray analysis [2].     

Photochemische Reaktionen. 43. Mitteilung [1]. UV.-Bestrahlung von N-Phenylurethan und N-Phenylthiourethan

Ultraviolet irradiation of N-phenylurethane (I) solutions with wavelength 253,7 nm resulted in the formation o polymeric material, the characteristic pattern of monomeric products associated with Photo-FRIES -type rearrangements [→ ethyl anthranilate (II), ethyl p-aminobenzoate (III)], and accompanying dissociation products [→ aniline (IV)]. N-Phenylthiourethance (V) showed no tendency to undergo Photo-FRIES -type rearrangements. Formation of polymeric material and aniline (IV), and in the presence of molecular oxygen, cyclodehydrogenation to the 2-ethoxy-benzthiazol (VI) as well as a ready exchange of the sulfure atom in V by oxygen occurred instead.     

Citrus-Carotinoide. 1. Mitteilung. Synthese von Apocarotinoiden mit einer anders gelagerten Methylgruppe; Strukturaufklärung von Citrus-Carotinoiden

Synthesis of Apocarotenoides with a Shifted Methyl Group; Structure Elucidation of Citrus-Carotenoides With regard to the investigation of the biosynthesis of the C₃₀-carotenoids in citrus fruits apocarotenoids with a methyl group shifted by one position (diapocarotenoids) were synthesized. Characteristical differences, especially in the 270-MHz-¹H-NMR. spectra between the apo- and the diapocarotenoids are reported. The comparison of the natural pigments with the synthetic compounds proves that the natural products belong to the apocarotenoids as has been postulated earlier.     

Stoffwechselprodukte von Mikroorganismen. 218. Mitteilung. Versuche zur Strukturaufklärung von Niphimycin, 1. Teil. Reinigung und Charakterisierung der Niphimycine Iα und Iβ sowie Abbau mit Salpetersäure

On the Structure Elucidation of Niphimycin, Part I. Purification and Characterization of the Niphimycins Iα and Ib?; Degradation by Nitric Acid From a sample of niphimycin the pure components, niphimycin Iα and Ib?, were isolated by column chromatography and droplet counter-current chromatography. They were characterized by UV., IR., ¹H-NMR. (300 MHz) and ¹³C-NMR. spectra. A vigorous degradation of niphimycin with nitric acid, followed by esterification with diazomethane, gave a complex mixture, from which many components could be isolated and identified. Several of the degradation products were synthesized, one of them (dimethyl 2,4-dimethyladipate) in a stereospecific manner, establishing the configuration of two of the centers of chirality of niphimycin. Niphithricin was identified with copiamycin and yielded with nitric acid a degradation mixture very similar to that from niphimycin. The structures of the degradation products are in good agreement with a macrolide-type structure of niphimycin and copiamycin. Further work for structure elucidation of niphimycin and copiamycin is in progress.     

Photochemische Reaktionen. 44. Mitteilung [1]. Zur Photochemie von gesättigten β-Ketosulfiden

Ultraviolet irradiation of the saturated β-ketosulfides 6 and 7 (direct n → π* excitation) in benzene and methanol solutions resulted mainly in the selective α-cleavage of the bond between C?O and C_α-S, producing ketenes by the well known hydrogen transfer as secondary reactions. Depending upon the availability of internal and/or external nucleophiles, the compounds 8 , 9 , 10 and 11 were formed as major products. The high yields in some of these light-induced transformations open an attractive synthetic approach to new heterocompounds.     

Die Cardenolide von Acokanthera oppositifolia (LAM.) CODD. 3. Mitteilung . Isolierung weitere Cardenolide und teilweise Strukturaufklärung. Glykoside und Aglykone, 301. Mitt.

The presence of 19 cardenolides in the extracts from the seeds of Acokanthear oppositifolia (Lam.) CODD could be traced by means of paper chromatography. Thirteen of these cardenolides could be isolated in crystalline form, acovenoside A (= 2) being by far the major component. Of the other 12 crystalline substances, 5 could be identified with known cardenolides: 2′ = acofrioside L, 3 = acolongifloroside H, 14 = acovenoside C, 15 = acolongifloroside K, 16 = ouabain. The substances 1′, 1″, 4, 6, 7, 8 and 13 are very probably new compounds. Four of these were given trivial names and the following structures were proposed: 1″ = oppovenoside, probably 10 ; 4 = oppofrioside ( 5 ); 6 = acotaloside ( 6 ); 13 = opposide, probably 12 , cf. following publication [21]. Furthermore, the structure 8 has been proposed for acolongifloroside H.