Stereocontrolled Synthesis of Pseurotin A2

Multicomponent Synthesis of 3(2H)-Furanones Initiated by Copper(II)-Catalyzed Alkyne-Carbonyl Cross Metathesis

The cooperative Lewis and Brønsted acid catalysis makes convergent synthesis of 3(2H)-furanones through a three-component coupling of 1,3-diynes, alkyl glyoxylates and water. Control experiments support that Lewis acid-catalyzed highly chemo-, regio- and stereoselective alkyne-carbonyl metathesis of 1,3-diynes and alkyl glyoxylates might be the initial step of this multicomponent annulation. Further chemo- and regioselective hydration of the alkyne-carbonyl metathesis product and subsequent oxa-Michael addition promoted by Brønsted acid results in the formation of two C-O bonds of the five-membered oxygen heterocycle.

Fungal Duel between Penicillium brasilianum and Aspergillus nomius Results in Dual Induction of Miktospiromide A and Kitrinomycin A

Cocultivation of the fungi Penicillium brasilianum MST-FP1927 and Aspergillus nomius MST-FP2004 resulted in the reciprocal induction of two new compounds, miktospiromide A (1) from A. nomius and kitrinomycin A (2) from P. brasilianum. A third new compound, kitrinomycin B (3), was also identified from an axenic culture of P. brasilianum, along with the previously reported compounds austalide K (4), 17S-dihydroaustalide K (5), verruculogen (6), and fumitremorgin B (7). The structures of 1-3 were elucidated by detailed spectroscopic analysis and DFT calculations, while 4-7 were identified by comparison to authentic standards. The genome of A. nomius MST-FP2004 was sequenced, and a putative biosynthetic gene cluster for 1 was identified. Compound 2 showed activity against murine melanoma NS-1 cells (LD99 7.8 μM) and the bovine parasite Tritrichomonas foetus (LD99 4.8 μM).

Biomimetic Total Synthesis and Investigation of the Non-Enzymatic Chemistry of Oxazinin A

We report the first total synthesis of an antimycobacterial natural product oxazinin A that takes advantage of a multi-component cascade reaction of anthranilic acid and a precursor polyketide containing an aldehyde. The route utilized for the synthesis of the pseudodimeric oxazinin A validates a previously proposed biosynthetic mechanism, invoking a non-enzymatic pathway to the complex molecule. We found a 76 : 10 : 9 : 5 ratio of oxazinin diastereomers from the synthetic cascade, which is an identical match to that found in the fermentation media from the fungus Eurotiomycetes 110162. Further investigation of the non-enzymatic formation of oxazinin A using 1 H-15 N HMBC NMR spectroscopy allowed for a plausible determination of the stepwise mechanism. The developed route is highly amenable for the synthesis of diverse sets of analogs around the oxazinin scaffold to study structure-activity relationships (SAR).