Practical Synthesis of Tricyclic Lactam Model of Antitumor Renieramycin-Saframycin Natural Products
摘要:
practical synthesis of the tricyclic lactam model compound of antitumor renieramycin-saframycin natural product starting from 2-hydroxy-4,5-dimethoxy-3-methylbenzaldehyde in eleven steps was described. A tosyl group was used for protection of a phenol during this transformation. The overall yield of the target compound was 23%.
An improved totalsynthesis of (±)-renieramycin G (1g) from readily available 2-hydroxy-3-methyl-4,5-dimethoxybenzaldehyde (7) in 21 steps (6.3% overall yield) is described. The synthesis features the concise construction of a pentacyclic framework using the stereoselective Pictet–Spengler type cyclization reaction of lactam (25) with ethyl diethoxyacetate, followed by the base-catalyzed epimerization
Model compounds of the left-half of renieramycins, which are anticancer marine natural products having an alpha-aminonitrile functionality, were prepared from phenylalanine derivatives. The key step of the transformation is the stereospecific construction of 1,3-cis stereochemistry via an exomethylene intermediate. The stereoselective alpha-aminonitrile formation under kinetically controlled conditions is also discussed. The initial cytotoxicity profiles are presented. (C) 2014 Elsevier Ltd. All rights reserved.