Talaromyces stipitatus

Talaromycin B is a spiro-acetal produced by the fungus Talaromyces stipitatus, the toxicity of which may be due to its ability to block outward potassium fluxes. In an elegant synthesis, the requisite open-chain polyol with hydroxy groups in the y-and y -positions was assembled from nitrile oxide and olefin building blocks 50 and 51, both of which carry a f>w(hydroxyethyl) moiety protected as a cyclohexanone acetal (284). Hydrogenolysis of the N O bond of isoxazoline 52 using Raney nickel, followed by treatment with aqueous acid, gave the spiroketal 53, which was further transformed into racemic talaromycin B (54) (Scheme 6.54) (284). 

Mandalari, G., Bisignano, G., Lo Curto, R. B., Waldron, K. W., and Faulds, C. B. (2008). Production of feruloyl esterases and xylanases by Talaromyces stipitatus and Humicola grisea var. thermoidea on industrial food processing by-products. Bioresour. Technol. 99, 5130-5133. 

Talaromycins. A group of epimeric spiroketals from cultures of Talaromyces stipitatus (Penicillium stipi-tatum). C12H22O4, Mr 230.30, oil. T. belong to the my-cotoxins and possess antibiotic properties. 

The recent example of talaromycins A and B (Fig. 2.40) produced by the tox-icogenic fungus Talaromyces stipitatus illustrate the strategic utilization of sophisticated spectroscopic techniques in structure determination (239). These two toxins were isolated as a mixture and were extremely difficult to resolve. Due to the loss of water in the positive CI-MS, the molecular ions of these diastereomers were detected only by NCI-MS, with deuterium exchange NCI-MS confirming the presence of two exchangeable protons. The coupling connectivities of the individual diastereomers were mapped with a COSY spectrum (Fig. 2.40). The purified compounds were ultimately separated after formation of their phenyl boronic acid esters (Fig. 2.41). 

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