Talaromyces stipitatus Talaromycins

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). 

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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