The structural architecture present in marine toxin azaspiracid - 20 stereocenters, 9 rings, 3 separated spirocenters - has attracted considerable synthetic attention. Our efforts toward the synthesis of azaspiracid have led to the completion of both C₁-C₂₆ northern and C₂₇-C₄₀ southern halves. Herein, the
synthesis of southern FGHI ring system...
Coibamide A is a methyl-stabilized cyclic depsipeptide with a lariat side chain that was isolated from a marine cyanobacterium as part of an International Cooperative Biodiversity Groups program based in Panama. Previous testing of this potent and selective growth-inhibitory agent in the National Cancer Institute (NCI) in vitro 60 human...
This thesis describes the chemical investigation of marine cyanobacteria collected in Madagascar and Panama with an emphasis on the isolation and structure elucidation of medicinally relevant secondary metabolites.
A collection of the marine cyanobacterium Lyngbya majuscula from the Radames Islands, Madagascar yielded two new cyclic depsipeptides, radamamides A and B,...
Our quest for pharmaceutically important marine natural products led to re-isolation of known mandelalides A-D and identification of new congeners E-L from re-collected South African Lissoclinum tunicate specimens. Mandelalides A, B, and L were characterized as selective cancer cell toxins, with an unusual activity profile influenced by their glycosylation /...
Coibamide A is a highly methylated cyclic depsipeptide isolated from Panamanian marine filamentous cyanobacteria as part of an International Cooperative Biodiversity Groups (ICBG) program based in Panama. This structurally unique agent exhibits potent cancer cell toxicity with an unprecedented selectivity profile in the National Cancer Institute (NCI) 60 cell line...
Metagenomics has revealed that the marine microbial biosphere is immensely more diverse than originally considered, and is an almost untapped reservoir for the potential discovery of microbial natural products. Despite numerous advances in culturing, biosynthetic engineering and genomic-based screening efforts to uncover much of this diversity in relatively accessible environments,...
Studies towards the total synthesis of (+)-Phomactin A (1), D (6), and G (9), fungal metabolites with unique molecular architecture and pronounced biological activity, are described. These studies resulted in the synthesis of advanced intermediates 354 and 356, which contain all of the carbon atoms of 1, 6 and 9....
Microbial natural products represent a massive repository of unique chemical scaffolds with corresponding diverse biological functions. However, in the past decade the development of natural products into new therapeutics has dwindled, in part due to the challenges posed by high rediscovery rates and low throughput associated with classical bioassay-guided fractionation...
This thesis is an investigation of the natural products deriving from marine algae and cyanobacteria and has resulted in the discovery of eleven new secondary metabolites. The structure elucidations of these new molecules were performed using a variety of spectroscopic techniques. Four new macrolides were isolated and characterized from the...