Syntheses of pseudoceramines AD and a new synthesis of spermatinamine, bromotyrosine natural products from marine spongesElectronic supplementary information (ESI) available: 1H and 13C NMR spectra for compounds 25, 13, 14, 1719, 21, 2633, and 1H NMR spectrum for compound 34. See DOI: 10.1039/c1ob06722b

Herein we report the total syntheses of pseudoceramine A-D ( 25 ) and spermatinamine ( 1 ) isolated from the marine sponge Pseudoceratina sp. Direct acyl substitution of -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. The total syntheses of five bromotyrosine alkaloid natural products have been achieved, utilising a direct acyl substitution of -hydroxyiminoesters with amine nucleophiles as the key transformation.