Prianosins isolation

A family of alkaloids characterized by a pyrroloquinone skeleton has been isolated in recent years from several sponges. Included in this family are the batzellines, isobatzellines, damirones, makaluvamines, discorhabdins, prianosins and wayakin. These alkaloids have shown a... 

The sulfide marine metabolites having a pyrroloquinoline skeleton can be divided into three groups the batzellines-isobatzellines, the prianosins-discorhabdins, and the makaluvamines. All of these types of compounds have been isolated from sponges. 

These complex sulfide-containing pyrroloiminoquinone alkaloids consist of the prianosins A-D (52, 53, 56, 57), isolated from the Okinawan Prianos melanos [54, 55], the discorhabdins A and B (52, 54), obtained from three different species of the New Zealand Latrunculia [56], discorhabdin D (57) from Latrunculia brevis and Prianos sp. [57], and discorhabdin Q (55), from Latrunculia purpurea, and several species of... 

The alkaloids containing the pyrroloquinolinequinoneimine subunit isolated so far are called discorhabdins (481-486) and prianosins (481, 484, 487,488). They are very similar natural products that are examined together. 

Some of the compounds that were isolated and named by independent groups were later noticed to be actually the same compounds. Thus, discor-habdin A (481) and discorhabdin D (484) are identical with prianosin A and prianosin D, respectively. 

Although their isolation, characterization, and biological activities are reviewed individually, synthetic studies toward discorhabdin and prianosin are examined under the same topic because each synthetic study is closely related to both groups of alkaloids. 

In 1987, Kobayashi et al. reported on the isolation of a novel alkaloid, prianosin A (481), from the Okinawan marine sponge Prianos melanos (204). The methanol-toluene extract of the green sponge, which was collected at a depth of 2 to 3 meters in the Motobu Peninsula of the Okinawa Island, was partitioned between toluene and water. The water layer was extracted with chloroform and extensive column chromatography afforded prianosin A (481) (0.02%, wet wt.). 

S, T, and U [29] possess methyl sulfide moieties, discorhabdin W [30] is a dimeric structure linked by a disulfide bond, while other members of this series do not contain sulfur. Furthermore, discorhabdins F [31], Q, S, and T and prianosin B contain a 16,17-dehydropyrroloiminoquinone moiety. The enantiomeric pairs of discorhabdins B, G /I, L, and W were also isolated from Latrunculia species sponges [32]. A study focusing on the elucidation of the absolute stereochemistry of several discorhabdins was reported by Copp et al. [33]. 

Sequences for the synthesis of the more complex discorhabdins, discorhabdin A and prianosin B, have been developed only in our laboratoiy. Discorhabdin A, which has a unique sulfur-containing fused ring structure, incorporating azacarbocyclic spirocyclohexanone and pyrroloiminoquinone systems, displays the most powerful cytotoxic activity among isolated members of the discorhabdin family. 

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