Snider named ACS Fellow

Charles A. Breskin Professor of Organic Chemistry Barry Snider has been named a Fellow by the American Chemical Society (ACS). ACS members are selected as fellows to recognize and honor their outstanding achievements in and contributions to science, the profession, and ACS. Fellows will be inducted at the ACS National Meeting in Denver on Aug. 29. Snider’s work in recent years has focused on total synthesis of natural products, a dazzling array of which are shown on his website: Recent stories on this blog discussing new syntheses from the Snider lab include:



Biomimetic Route to Maldoxin

In their recent Organic Letters paper entitled the Syntheses of Chloroisosulochrin and Isosulochrin and Biomimetic Elaboration to Maldoxin, Maldoxone, Dihydromaldoxin, and Dechlorodihydromaldoxin, the Snider lab at Brandeis developed an efficient biomimetic synthesis of maldoxin (4), the biological precursor of several cytotoxic natural products recently isolated from the plant endophytic fungus Pestalotiopsis fici. Chloroisosulochrin (1) was synthesized for the first time and elaborated to maldoxin (4) by a three-step biomimetic route consisting of oxidative cyclization to give spirofuranone 2, acid catalyzed ring opening to yield dihydromaldoxin (3) and a second oxidative cyclization to form maldoxin (4).

Electrophilic chlorination of phenols usually takes place unselectively at both ortho and para positions.  For the synthesis of chloroisosulochrin, they developed an ortho selective chlorination using 2,2,6,6-tetramethylpiperidine and sulfuryl chloride.  Presumably a hindered N-chloroamine is formed, which hydrogen bonds to the phenol and delivers electrophilic chlorine intramolecularly.

An alternative to scuba diving

Many promising medicinal agents (anti-cancer, anti-bacterial, anti-viral and anti-fungal) have been discovered among the diverse molecules produced by marine organisms. However, scuba-diving to harvest sponges and algae is not usually a practical way of obtaining usable quantities of these compounds, especially if they are present only in trace quantities in the source organisms.

A recently published paper in Organic Letters from the laboratory of Assistant Professor of Chemistry Isaac Krauss is the first to present a synthetic laboratory approach to the preparation of the bromophycolides, originally isolated from Callophycus Serratus, a red algae which was collected off the coast of Fiji. Although these compounds were shown to posses anti-tumour, anti-HIV and anti-malarial properties, algae collected in a second expedition to Fiji apparently contained none of the natural product (hence the desirability of a laboratory synthesis). The bromophycolides are a structurally unique family of natural products containing brominated asymmetric carbon centers and large 19-membered rings. This paper illustrates the preparation of the bromophycolide A and D ring system in high enantiomeric purity via a short (9-step) synthetic sequence.

Finding novel antibiotics in dirt using unculturable bacteria

Sean Brady from The Rockefeller University will be visiting campus to lecture on Culture Independent Approaches for the Discovery of New Bacterial Metabolites as part of the Joint Biology/Biochemistry Colloquium Series, Wednesday, Oct 13, at 4:00 pm in Gestenzang 121.

Sean’s research centers on the discovery, biosynthesis and characterization of new, genetically encoded small molecules from microbial sources, with a special focus on soil bacteria and pathogenic bacteria. One area of particular interest is the development of methods to access new biologically active small molecules from bacteria that cannot be grown in culture. Soil bacteria that can’t yet be cultured outnumber those that have been by orders of magnitude, and provide a huge pool of genetic diversity that can be searched for novel useful natural products.

Sean is a Howard Hughes Medical Institute Early Career Scientist. He was named a Searle Scholar, an Irma T. Hirschl Scholar, an Alexandrine and Alexander L. Sinsheimer Scholar and an Arnold and Mabel Beckman Young Investigator.

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