Extending Pummerer reaction chemistry. Synthesis studies in the phakellin alkaloid area

The syntheses of (+/-)-dibromophakellstatin and, from this species, (+/-)-dibromophakellin are described. Oxidative cyclization of a phenylthiolated dihydrooroidin derivative triggered by a Pummerer reaction constitutes the key step in this biomimetic approach to this family of marine alkaloids.     

尖山橙生物碱的研究

从尖山橙(Melodinus fusiformis)全植物中分得15个生物碱, 其中三个为新生物碱,采用波谱分析和化学方法,它们的结构分别鉴定为: 11,19(R)-dihydroxy tabersonine,11-hydroxy-14,15a-epoxy tabersonine 和 scandine N~b-oxide。其余12个为已知生物碱: scandine, moloscandonine, 10-hydroxysoandine, Kopsinine,15α-hydroxydopsinine, venalstonine, tabersonine,11-methoxytabersonine, 11-hydroxytabersonine, tubotaiwine(13), vindolinine (14)和deacetylpicraline。新生物碱1和2分别显示有明显的抗生育和抗肿瘤的作用。     

Synthesis of the racemic alkaloid diptocarpilidine

A convenient approach to the synthesis of the racemic alkaloid diptocarpilidine from the readily available l-hydroxy-7-thiaoctane has been developed.Institute of Chemistry, Bashkir Scientific Center, Urals Branch Academy of Sciences of the USSR, Ufa. Institute of Chemistry of Plant Substances, Academy of Sciences of the Ubzek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 261–263, March–April, 1991.     

Synthesis of the isoindolobenzazepine alkaloid lennoxamine

The naturally occurring isoindolobenzazepine lennoxamine (1) has been synthesised from 6-bromopiperonal in 9 steps by a route which involves formation of the 2-arylbenzazepine (10) from the azide (9) as the key step.     

Synthesis of the racemic alkaloid diptaline

The isolation from the plantDipthychocarpus strictus (Cruciferae) of the optically active base diptaline, identified as N-(11-methylsulfinylundecyl)urea, has been reported [1]. A synthesis of the racemic form of this alkaloid has now been achieved.Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 102–105, January–February, 1992.     

Synthesis of the marine alkaloid caulersin

A three-step synthesis of caulersin (3) from indole-2-acetic acid methyl ester and indole-2-carbonyl chloride is described. As the spectral data of the synthetic sample differed from those reported for the natural product, the structure was determined by X-ray crystallography.     

Synthesis of the spirocyclic alkaloid nitramine

The alkaloid nitramine was prepared in a four operation process using reductive cyclization of a γ-cyano ester to a spirolactam as a key step.     

Synthesis of N-aminoglycosides on the basis of the d-pseudoephedrine alkaloid

Russian Journal of General Chemistry -     

Synthesis of N-aminoglycosides of the alkaloid cytisine

A series of new N-aminoglycosides of the alkaloid cytisine based on industrially available monosaccharides D-glucose, D-galactose, D-xylose, and L-arabinose was synthesized and characterized. The optimal methods for condensing and isolating the products were found. The structures and position of cytisine in the glycosides were proved by PMR spectroscopy. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 596–597, November–December, 2008.     

Synthesis of the Arctic sponge alkaloid viscosaline and the marine sponge alkaloid theonelladin C

The synthesis of Arctic sponge alkaloid viscosaline (1) is achieved by using the Zincke reaction as the penultimate step. A key synthetic intermediate theonelladin C (6), itself a marine sponge natural product, is synthesised efficiently using a four-step sequence.     

Further studies of the Daphniphyllum alkaloid polycyclization cascade

The scope of the 2-azadiene intramolecular Diels-Alder cyclization, previously employed for synthesis of the Daphniphyllum alkaloids, has been further investigated. Through a series of 1,5-diol cyclization precursors the substitution pattern of both the dienophile and the 2-azadiene were examined. From these studies it was shown that the cascade reaction is tolerant toward a variety of alkyl-substituted dienophiles. However, it was also demonstrated that this reaction is very sensitive to the substitution pattern of the 2-azadiene. Alterations made to the structure of the 2-azadiene cause either competing side reactions or complete failure of the reaction cascade.     

Cycloaddition studies directed toward the strychnos alkaloid minfiensine

The thermolysis of several imidofuranyl carbamates delivers products derived from an intramolecular [4+2]-cycloaddition reaction. In the case of the ortho-azido aryl carbamate 13, the preferred path proceeds by an electrocyclization of a nitrene intermediate to produce a 3-substituted indole. Attempts to reduce the azido group resulted in a novel intramolecular aza-Wittig reaction with the neighboring imido group.     

Synthetic studies and biosynthetic speculation on marine alkaloid chartelline

Synthetic studies and biosynthetic speculation on chartelline inspired by an unexpected reaction are described.     

Synthesis of the isoquinoline alkaloid, crispine C

The first total synthesis of the isoquinoline alkaloid, crispine C is described in seven steps using a Henry reaction and the Pictet-Gams variant of the Bischler-Napieralski reaction to effect the key transformations.     

Synthesis of the novel isoquinoline enamide alkaloid polycarpine

The synthesis of the novel enamide isoquinoline alkaloid polycarpine, (Z)-1-(2′-hydroxy-3′,4′-dimethoxy-benzylidene)-3,4-dihydro-6,7-dimethoxy-2-(1H)isoquinolinecarboxaldehyde, proceeding from commercially available 2′,3′,4′-trimethoxyacetophenone in seven steps is described. The O-methyl and O-benzyl derivatives were also obtained.     

A Novel Alkaloid from Melodinus henryi

The isolation and structure elucidation of a novel alkaloid, namely of the 14‐O‐ethyl‐substituted (3α,14α,16α)‐2,7‐secoeburnamine derivative 1 from the leaf of Melodinus henryi is reported. Ten known alkaloids were also isolated. Their structures were determined spectroscopically. The isolates were evaluated for their cytotoxicity.