Decahydroquinoline derivatives

Lepadins constitute a class of recently discovered antimalarial marine alkaloids. These molecules are decahydroquinoline derivatives bearing a linear eight-carbon chain isolated from two marine invertebrates of Australian origin, Clavelina lepadiformis [49] and Didemnum sp. [50]. 

In the quinoline ring system, the heterocyclic ring is more easily reduced than the benzene ring, forming tetrahydro-compounds or even decahydroquinoline derivatives under hydrogenation conditions. Quinolines have also been reduced to 1,2,3,4-tetrahydroquinolines by zinc borohydride and dimethylaniline under sonication conditions or with indium metal in... 

Other unsuccessful approaches to perhydrohistrionicotoxins have been reported (Schemes XXXVI, XXXVII). 259, 260). In one study an unexpected rearrangement of a spiro ring occurred during attempted ketalization (Scheme XXXVII, reaction C). A sequence involving first ring opening and then recyclization was proposed. The rearrangement product, a hexahydroquinoline, was reduced to a decahydroquinoline derivative and acetylated. 

Each of the three decahydroquinoline sulfonates shown below gives a different product composition on solvolysis. One gives 9-methylamino-E-non-5-enal, one gives 9-methylamino-Z-non-5-enal, and one gives a mixture of the two quinoline derivatives 14-D and 14-E. Deduce which compound gives rise to which product. Explain your reasoning. 

At -61°C the H-NMR spectrum of /V-methyl-cis-octahydrocarbostyril shows signals for 8a-H in both conformers 167 and 168. On this basis Wi values were recorded from room-temperature spectra of a variety of derivatives existing as equilibria. The N-inside conformation was preferred for the JV-H compound, whereas the N-outside conformation was preferred for the N-Me compound. This is different from the situation in N-methyl-cis-decahydroquinoline and may be due to a closer approach of N-Me to the C-8 methylene in 167 than in 160 as a result of a flattened sp2-hybridized nitrogen atom.211... 

Alkali metal in ammonia reductions of pyrrolobenzodiazepine-5,11-diones give trans-2-aminocyclohexanecarboxylic acid derivatives (e.g., 4) in enantiomerically pure form.2 3 A method for preparation of cis-2-aminocyclohexanecarboxylic acids related to 4 is based on the enantioselective hydrolysis of symmetrical diesters with pig liver esterase.4 cis-2-Aminocyclohexane derivatives have been used for syntheses of aminocyclitol antibiotics.4 5 6-Alkyl-cis-2-aminocyclohexanecarboxylic acids can be prepared by alkali metal in ammonia reduction of pyrrolobenzodiazepine-5,11-diones followed by olefin hydrogenation the cis-decahydroquinoline alkaloid (+)-pumiliotoxin C has been prepared by this methodology.2... 

A number of other dendrobatid alkaloids appear to be decahydroquinolines based on spectral and chemical properties. All of these alkaloids are secondary amines no simple N-alkyl derivatives have been found. FTIR spectra are not yet available for many of these alkaloids. Many decahydro-... 

Gephyrotoxins are unique in Nature to amphibians and, indeed, occur only in certain populations of the extremely variable Colombian poison frog, Dendrobates histrionicus (1). Gephyrotoxin might be derived by cyclization of a c/.r-decahydroquinoline having a trans orientation of the... 

Decahydroquinoline and decahydroisoquinoline are dehydrogenated over palladium to the corresponding (>z-tetrahydro derivatives, a valuable procedure for making these compounds. 1-Methylisoquinoline is prepared by refluxing its 3,4-dihydro derivative with excess Raney nickel until the temperature reaches 248°, the boiling point of the desired product (75%). 

W-phenoxycarbonyl bicyclic enone, which was structurally similar to 61, exclusively provided a cw-annulated octahydroquinoline derivative. From the trans-annulated decahydroquinoline 62, fraw5 -4a-e/7t-pumiliotoxin C 63 was S5uithesized in a 5-step reaction sequence, including hydrogenolytic desulfurization of the dithiolane prepared by treatment of the carbonyl group in 62 with 1,2-ethanedithiol. 

Ehrenstein and Bunge (265) found that the derivatives of cis-decahydroquinoline and cis-decalin are more easily dehydrogenated than the corresponding trans forms according to these authors, the facts found by them are in conformity with the multiplet theory. 

Bicyehe nitrogen-containing heterocyclic compounds were also fluorinated by ECF. ECF of AT-methyl-decahydroquinoline forms a mixture of cis- and tra/j5-isomerie perfluorinated derivatives. Ring contraction and formation of per-fluorocyclohexanes are side processes. Trows-quinolizidine gives perfluoro-tra/w-quinolizidine (yield 16-23%) and a large amount of other compounds with unknown... 

Some n.m.r. studies on cis- and /ra s-decahydroquinolines and their acyl derivatives lead to the conclusions that (i) the troiw-isomer has a twin-chair conformation (ii) the cw-isomer (31) prefers the twin-chair... 

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