Untersuchungen an 1.4‐Naphthochionen, 15. Mitt. Reaktion von 2‐ und 3‐Chlor/Bromjuglonderivaten mit methanolischer Lauge (Teil 1: Monomere Produkte)

Abstract

Die 2-und 3-Chlor-bzw. Bromjuglone 1-4 reagieren in methanolischer Natronlauge nicht regiospezifisch zu den entsprechenden Hydroxyjuglonen 5 und 6, sondern uber die intermediar gebildeten Methoxyderivate 7 und 8 zu Gemischen aus 5 und 6 rnit unterschiedlicher Regioselektivitat. Die analoge Reaktion der 2.3-Dichlor-bzw. Dibromjuglonderivate 14 und 15 fiihrt stets zu gleichen Gemischen aus 16a/b und ' I7a/b, die rnit Bu,SnH in einem Schritt strukturbeweisend in 7 bzw. 8 uberfuhrt werden. The 2-and 3-chloro-or bromojuglone derivatives 1-4 do not react regiospecific ally with sodium hydroxide in methanol to yield the analogous hydroxyjuglone derivatives 5 or 6. Rather, mixtures of 5 and 6 are obtained via the methoxy derivatives 7 and 8. The corresponding reactions ofthe 2.3-dichloro-and dibromojuglone derivatives 14 and 15 always lead to the same mixtures of 16db and 17db. The structures of these products were established by halogen elimination with Bu,SnH which leads to the known compounds 7 and 8.Die alkalische Hydrolyse von 2-bzw. 3-Chlor-1.4-naphthochinonderivaten mit wa13riger Natronlauge in Methanol ist eine Standardmethode zur Darstellung von 2-bzw. 3-Hydroxy-1.4-naphthochinonderivaten. Setzt man die entsprechenden Chlorjuglone 12) und 32) (Abb. 1) ein, so stellt man bei der Synthese von 3.5-Dihydroxy-1.4-naphthochinon (6) besonders schlechte Ausbeuten fest. Wird das Verfahren auf die analogen Bromjuglone 22) und 4*) iibertragen, so zeigt sich, da13 stets Gemische aus 2-und 3-Hydroxyjuglon (5 und 6) im Verhaltnis 1:l entstehen, bei 4 wieder in sehr geringer Gesamtausbeute. Da sich 2-bzw. 3-Hydroxy-1.4-naphthochinone wegen intensiver Komplexbildung an Kieselgel chromatographisch nicht trennen lassen, erfolgte die Quantifizierung durch Abschatzung der Integralstufen der 'H-NMR Signale fur die 5-OH Funktion bei 6 = l l ppm (3-Hydroxyjuglon) und bei 6 = 12.3 ppm (2-Hydroxyjuglon).Die daraufhin durchgefiihrte Nachuntersuchung der Reaktion rnit den beiden Chlorjuglonen 1 und 3 ergab, da13 auch in diesen Fallen keine Regiospezifitat, sondern lediglich eine stark ausgepragte Regioselektivitat vorliegt (Abb. 1). Bei der dc Untersu-+) Meinem verehrten Lehrer, Prof. Dr. Helmut Loth, zum 60. Geburtstag gewidmet.

Synthesis and Evaluation of Antimicrobial and Cytotoxic Activity of Oxathiine-Fused Quinone-Thioglucoside Conjugates of Substituted 1,4-Naphthoquinones

“…Bromination of available hydroxyjuglone derivatives 7 and 8 in chloroform solution according to the work in [ 28 ] led to bromoquinones 9 and 10 in good yields, 92%. Subsequent treatment of quinones 9 and 10 in 1,4-dioxane with 0.2 M ethereal diazomethane solution and crystallization from MeOH gave a second pair of initial bromomethoxyjuglones 11 and 12 in yields 85% ( Scheme 2 ), which were identical to such compounds described in [ 29 ].…”

Antibacterial Paramagnetic Quinones from Actinoallomurus

“…Overall, the MS data, the absence of one aromatic proton and of one methoxy group in 2 (or one methylamino in 1), are in agreement with a terminal quinone moiety oxidatively cleaved and replaced by two carboxylic acids as reported in the literature. 15,16 Sufficient incorporation into paramagnetoquinones of 13 Clabeled precursor(s) took some media design efforts, since attempts failed in a minimal medium suitable for growth of and paramagnetoquinone production by strain ID145113 (see Experimental Section). We thus resorted to remove and/or replace individual components from the complex AF-A production medium in order to render it closer to a chemically defined medium.…”

“…Strain ID145113 was thus cultivated in 200 mL of AF-N medium containing 13 C-[U]-glucose. LC-MS analysis indicated that paramagnetoquinones were about 80% enriched in 13 C. Purification as described above led to 45 mg of the 1/2 mixture, which was then treated with H 2 O 2 to obtain 13 C-labeled 5.…”

“…NMR analysis (HSQC, HMBC, together with 13 Antibacterial Activities. The antibacterial activities of the mixture 1/2 are reported in Table 3.…”

En Route to D-Ring Inverted Phorbol Esters

“…o -Vanillin ( 12 ) was reduced via a Wolf–Kischner reduction to the corresponding phenol ( 13 ), which underwent a salcomine ( 14 ) oxidation to afford quinone 15 in 88% yield over two steps . The methoxy group (i.e., 15 ) was exchanged for an isopropoxy ( 16 , 74%) in view of the fact that isopropyl ethers can be directly converted to acetyl groups . A Diels–Alder reaction involving cyclopentadiene was employed to protect the double bond carrying the methyl group, which proceeded with total stereoselectivity (i.e., 17 ).…”