Chemie von α-Aminonitrilen. Aziridin-2-carbonitril photochemische Bildung aus 2-Aminopropennitril

The English Footnotes (*) referring to Schemes 1-6 are intended to provide an extension of this summary. In the Footnote (*) to Scheme 5, a definition of the term ‘chirogenic reaction step’ is given. 2-Aminopropenenitrile in solvents such as MeCN, MeOH, or H₂O is photoisomerized by UV light to racemic aziridine-2-carbonitrile (rac- 2 ); the larger part of the starting material, however, fragments to HCN and MeCN. The observed photocyclization constitutes a structural connection within an ensemble of C₃H₄N₂ compounds considered to be potentially relevant to prebiotic chemistry.     

Ammoniakverlust aus α,ω-Alkandiaminen im Massenspektrometer. 22. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

Loss of ammonia from α,ω-alkanediamines in the mass spectrometer . Under electron impact α,ω-alkanediamines lose ammonia from the molecular ion. This fragmentation reaction is explained in the case of 1.4-butanediamine ( 1 ) on the basis of the spectra of homologues and deuteriated derivatives. The reaction proceeds via neighbouring group participation; the mechanism is given in Scheme 1.     

Chemie von α-Aminonitrilen. Aziridin-2-carbonitril,ein Vorläufer von rca-O3-Phosphoserinnitril und Glycolaldehyd-phosphat

Chemistry of α-Aminonitriles. Aziridine-2-carbonitrile, a Source of Racemic O′-Phosphoserinenitrile and Glycolaldehyde Phosphate Racemic aziridine-2-carbonitrile (rac- 1 ) in MeCN solution reacts regioselectively (> 90%) with 2 equiv. of T_sOH at room temperature to form the hydrotosylate of racemic O3-tosylserinenitrile (rac- 2 ) via β-ring opening (Scheme 2). A similar regioselective reaction takes place between rac-l and H₃PO₄ to produce racemic O₃-phosphoserinenitrite (rac-3) which is in turn a source of glycolaldehyde phosphate (=formylmethyl dihydrogenphosphate) under the conditions of a ‘retro-Strecker’ reaction in aqueous solution (Scheme 6). These experiments document a close structural relationship between the simplest of the sugar phosphates and an α-aminonitrile precursor. The English Footnotes (*) referring to Schemes 1-7 are intended to provide an extension of this summary.     

Synthesen von Mannich-Basen von Hydroxy-indolen. 3. Mitteilung über synthetische Indol-Verbindungen [1]

The reactivity of hydroxy-indoles under the conditions of the Mannich-reaction has been studied. The electrophilic side-chain enters in each case in a position ortho to the phenolic group. 4-Hydroxy-indole is substituted in the 5-, 5-hydroxy-indole in the 4-, 6-hydroxy-indole in the 7-, and 7-hydroxy-indole probably in the 6-position. The structures of the Mannich bases from 4-, 5- and 6-hydroxy-indole have been confirmed by comparison of the hydroxy-methyl-indoles obtained by reductive desamination with hydroxy-methyl-indoles prepared by unambiguous total synthesis.     

Photochemie von tricyclischen β, γ-γ′, δ′-ungesättigten Ketonen. 50. Mitteilung über Photoreaktionen

Photochemistry of tricyclic β, γ-γ′, δ′-unsaturated ketones The easily available tricyclic ketone 1 (cf. Scheme 1) with a homotwistane skeleton yielded upon direct irradiation the cyclobutanone derivative 3 by a 1,3-acyl shift. Further irradiation converted 3 into the tricyclic hydrocarbon 4 . However, acetone sensitized irradiation of 1 gave the tetracyclic ketone 5 by an oxa-di-π-methane rearrangement. Again with acetone as a sensitizer the ketone 5 was quantitatively converted to the pentacyclic ketone 6 . The conversion 5 → 6 represents a novel photochemical 1,4-acyl shift. The possible mechanisms are discussed (see Scheme 7). The tricyclic ketone 2 underwent similar types of photoreactions as 1 (Scheme 2). Unlike 5 the tetracyclic ketone 9 did not undergo a photochemical 1,4-acyl shift. The epoxides 10 and 14 derived from the ketones 1 and 2 , respectively, underwent a 1,3-acyl shift upon irradiation followed by decarbonylation, and the oxa-di-π-methane rearrangement (Schemes 3 and 4). The diketone 18 derived from 1 behaved in the same way (Scheme 5). The tetracyclic diketone 21 cyclized very easily to the internal aldol product 22 under the influence of traces of base (Scheme 5). Upon irradiation the γ, δ-unsaturated ketone 24 underwent only the Norrish type I cleavage to yield the aldehyde 25 (Scheme 6).     

Beitrag zur Massenspektrometrie substituierter α, ω-Alkandiamine. 29. Mitteilung über massenspektrometrische Untersuchungen

Contribution to the mass spectrometry of substituted α,ω-alkane diamines The main mass spectral fragmentation pattern of compounds of types 1 to 4 is discussed. After loss of C₆H₅ · CH₂ · from the molecular ion the acid correspondin to the N,N-disubstituted residue is splitted off. The mechanism of this fragmentation reaction depends on the member of CH₂-groups between the two nitrogen atoms (Schemes 1 and 3) and on the substitution pattern of both nitrogens (Scheme 2).     

Über die 1,2-Verschiebung von Carbonestergruppen bei der Benzilsäureumlagerung von α,β-Dioxobuttersäure-estern. 25. Mitteilung über Reduktone und Tricarbonylverbindungen [1]

In the benzilic acid type rearrangement of t-butyl α,β-dioxobutyrate (VII) the intact t-butoxycarbonyl group is shifted to the β-carbonyl carbon atom.     

Fragmentierung von α,β-Epoxyketoximen zu Alkinonen. Über Steroide, 228. Mitteilung

The experimental details of the oxidoketone-alkynone fragmentation brought about by the treatment of steroidal α,β-oxido-oximes with hydroxylamine-O-sulfonic acid in alcaline solution at room temperature are presented together with a discussion of the mechanism of this reaction. Studies of a ring closure reaction transforming the fragmentation products back into the starting α,β-unsaturated ketones are discussed.     

Neuartige massenspektrometrische Zerfallsreaktionen bei α,ω-disubstituierten Alkanen. 15. Mitteilung über das massenspektrometrische verhalten von stickstoffverbindungen [1]

The mass spectral behaviour of α,ω-disubstituted alkanes and, especially, that of different N-substituted α,ω-diaminoalkanes has been investigated. It was found that the two amino groups which are separated by CH₂-groups can fragment only to a small extent indepently from each other. Yet those fragmentation reactions are predominant in which both functional groups participate. The main reactions of this type are:

• 1 Loss of the N-substituent (R) from the molecular ion, leading to the [M⁺—R]-ions.
• 2 Loss of NH₃, primary or secondary amines from the [M⁺—R]-ion in the case of monodi-, tri- and tetra-substituted diamino compounds respectively.
• 3 α-Cleavage to the non charged nitrogen atom by forming the ions
• 4 S_Ni-type fragmentation.

The mechanisms of these fragmentation patterns were deduced by using D-labelled derivatives, from metastabile peaks and high resolution mass spectrometry. These reactions seem to be typical for disubstituted alkanes.     

Umwandlung von Krötengiften (Bufadienoldien) durch Mikroorganismen IV. 7β-Hydroxybufalin, 7β-Hydroxyresibufogenin und 12α-Hydroxyresibufogenin. 16. Mitteilung über Reaktionen mit Mikroorganismen [1]

Bufalin ( 1 ) was transformed to 7β-hydroxybufalin ( 2 ) by an aqueous suspension of the mycelium of Absidia orchidis VUILL. (HAGEM. ). Incubation of resibuforgenin ( 9 ) under the same conditions yielded 12α-hydroxyresibufogenin ( 7 ) and, under changed conditions, another monohydroxylated derivative which possesses most likely the structure of 7β-hydroxyresibufogenin ( 10 ). The corresponding cardenolide 3-O-acetyl-14β, 15β-epoxy-14-anhydro-digitoxigenin ( 17 ) gave both the 7β- and the 12α-monohydroxylated derivatives 18 and 22 and another monohydroxylated product 21 of unknown structure. All microbial transformation products are new.     

α, β-Epoxyketon → Alkinon-Fragmentierung I: Synthese von exalton und rac - muscon aus cyclododecanon über synthetische methoden, 3. Mitteilung

Experimental details concerning some examples of the tosylhydrazone version of the α, β-epoxyketone → alkynone fragmentation as well as a discussion of this process are given.     

Zur Synthese des Ecdysons. II. Mitteilung über Insektenhormone Synthesen von 2β, 3β-Dihydroxy-6-keto-A|B-cis-Steroiden

Experiments towards a synthesis of ecdysone ( 1 ) ([22R]-2β, 3β, 14, 22, 25-pentahydroxy-5β, 14α-cholest-7-en-6-one) have led to 2β, 3β-dihydroxy-6-keto-5α-steroids. These could be epimerized to the corresponding 5β-series. The proposed configurational assignments are supported by physical data and chemical correlation.     

α-Alkylierung von β-Hydroxycarbonsäuren über 1,3-Dioxan-4-on-Enolate

Highly Diastereoselective α-Alkylation of β-Hydroxycarboxylic Acids Through Lithium Enolates of 1,3-Dioxan-4-ones From serine, β-hydroxyisobutyric acid (‘Roche’ acid) and β-hydroxybutyric acid, the dioxanones 1–6 were prepared. The generation of the enolates of type I with LDA at ?75° and alkylation gave products with trans-configuration whereas protonation of the 5-methyl-substituted enolate allowed access to the cis-configurated β-hydroxybutyric-acid derivative 12 . Hydrolysis gave the free β-hydroxy acids of ‘syn’-and ‘anti’-configuration. Alkylation of the 6-unsubstituted dioxanones 1 and 3 yielded predominantly products resulting from attack in the cis-position of the t-Bu group. The ‘reactive’ conformation of the enolates involved is tentatively derived from the product configuration. The selectivity of the alkylation is also discussed in terms of the results of an ab-initio calculation on the enolates M–P.