Guitarrins A–E and Aluminumguitarrin A: 5‑Azaindoles from the Northwestern Pacific Marine Sponge Guitarra fimbriata

Guitarrins A–E (1–5), the first natural 5-azaindoles, and aluminumguitarrin A (1a), the first aluminum-containing compound from marine invertebrates, were isolated from the sponge Guitarra fimbriata. The structures of these compounds were established using detailed analysis of 1D and 2D NMR data, mass spectra, and X-ray analysis of 1 and 1a. Compound 3 was proved to be a natural inhibitor of alkaline phosphatase.