Chemistry of renieramycins. Part 7: Renieramycins T and U, novel renieramycin-ecteinascidin hybrid marine natural products from Thai sponge Xestospongia sp.

Two new bistetrahydroisoquinoline marine natural products, renieramycins T (1) and U (2), were isolated from the Thai blue sponge Xestospongia sp. and their structures were elucidated by comparing spectral data with those of renieramycin M (3a) and ecteinascidin 770 (4a). These compounds are the first reported examples of novel ecteinascidin-renieramycin hybrid natural products. Renieramycin T (1) showed strong cytotoxicity to several human cancer cell lines, its IC₅₀ values ranging from 4.7 to 98 nM.     

Chemistry of renieramycins. Part 6: Transformation of renieramycin M into jorumycin and renieramycin J including oxidative degradation products, mimosamycin, renierone, and renierol acetate

The transformation of renieramycin M (1m) into renieramycin J (1j) and jorumycin (2) is presented along with the results of antiproliferative assay data. The chemical stability and the oxidative degradation of 2 and renieramycin E (1e) to generate simple isoquinoline alkaloids, such as mimosamycin (7), renierol acetate (12), and renierone (8) are also described.     

Preparation of renieramycin left-half model compounds

Model compounds of the left-half of renieramycins, which are anticancer marine natural products having an α-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 α-aminonitrile formation under kinetically controlled conditions is also discussed. The initial cytotoxicity profiles are presented.     

Chemistry of renieramycins. Part 9: Stereocontrolled total synthesis of (±)-renieramycin G

A 25-step stereocontrolled total synthesis of (±)-renieramycin G (1g) from readily available 2-hydroxy-3-methyl-4,5-dimethoxybenzaldehyde (3) is described. This synthesis features the concise construction of the pentacyclic framework using the stereoselective Pictet-Spengler type cyclization reaction of lactam (14) with ethyl diethoxyacetate, followed by the base-catalyzed isomerization of the C-1 stereo center.