Syntheses of pseudoceramines A-D and a new synthesis of spermatinamine, bromotyrosine natural products from marine sponges.

Herein we report the total syntheses of pseudoceramine A-D (2-5) and spermatinamine (1) isolated from the marine sponge Pseudoceratina sp. Direct acyl substitution of α-hydroxyiminoesters with amine nucleophiles was developed as a key transformation. The synthetic compounds confirm the reported structures and importantly gives access to non-symmetrical spermine based natural products carrying two different bromotyrosine building blocks. Our new synthesis of spermatinamine is two steps shorter and more efficient than the previously reported sequence.