Secalonic acids

Cole RJ, Cox RH. Secalonic acids. In Handbook of Toxic Fungal Metabolites. New York Academic Press, 1981a, pp 646 669. 

The bixanthenyl 55 which possesses the ring system of the secalonic acids has been obtained from the 7-bromoxanthene via the arylboronic ester and a subsequent Suzuki coupling <04JOC6830>. The anionic polycondensation of acetonaphthones 56 with homophthalates gives dibenzo[Z7j]xanthones and offers an approach to the naturally occurring hypoxyxylerone system <04SL2693>. 

Revised structures of secalonic acids A. B, C, D Hooper er at., Chem- Commun. 1971, 111 eufem, J. Chem. Soc. (C) 1971, 3580. Crystal and molecular structure of secalonic acid A C. C. Howard er al. J. Chem. Soc. Perkin Trans. I 1976, 1820. Identity of secalonic acid A with mtothein Yoshioka et al, Chem. Pharm. Bull 16, 2090 (1968). Biosynthesis of secalonic acid A I. Kurobane et al., Tetrahedron Letters 1978, 1379. Review of secalonic acids and other ergochromes Franck, Flasch in Fortschr. Chem. Org Naturst. 36, 151-206 (1973). 

Secalonic acid A, ergochmme AA(2,2 ) 6.6. 7, -tetrahy-(trO-1,1, 5/3, S d, 8,8 -h exa hy d roxy6a, 6 a-dimethyl-9,9 -dloxo-[2,2 -bixanthcne]-10ap, t O aft ( 5 H,5 Hi-di carboxylic acid dimethyl ester. Fine lemon -yellow needles from dioxane 4 petr ether 4 chloroform, mp 246-248 (dec) also reported as mp 260 (Yoshioka et al. loc. cit.). [ t)D —73 (CHClj). uv max (methanol) 247, 340 ntn (c 18,140, 31.200). pKDMF 8.7. Reedily soluble in pyridine, dimethylformamide. dioxane, moderately sol in chloroform, methylene chloride, acetone. Gives a wine-red color reactiou with 5% FeClj in methanol. 

Tetrahydro-l//-xanthene-l,9-diones, synthesised from cyclohexa-l,3-diones and 2-fluorobenzoyl chlorides, are efficient Michael acceptors, offering a route to 4a-substituted xanthone derivatives similar to the secalonic acid half unit (Scheme 12) <97JCS(P1)1819>. 

CAS 35287-69-5 (secalonic acid D) 60687-07-2 (secalonic acid F) 34I9-II-2 (ergochrysin A) 3I0I-51-7 (ergoflavin)]... 

Diversonol (97), a fungal metabolite, was isolated by Turner from Penicillium diversum and its structural motif has also been found in some mycotoxins such as secalonic acids with interesting biological activity. Therefore, the total synthesis of diversonol will also promote the total synthesis of these... 

Figure 5.3 Chemical structures of blennolide C and secalonic acid.

Anne C. Meister studied chemistry at the University of Karlsruhe (now Karlsruhe Institute of Technology (KIT)) from 2005 to 2010. She completed her diploma thesis with the title Synthesis of 4-hydroxy-5-methylcyclohex-2-enones as building blocks for the total synthesis of secalonic acids in the group of Prof. Stefan Erase in Karlsruhe. Since March 2010, she has been working on her Ph.D. thesis ( total synthesis of secalonic acids ) in the same group. 

Tetrahydroxanthones from fungi include the blennolides (895-901), dihydroglobo-suxanthone (931) (632), diversonol (932) and the diversonolic esters (972, 973) (Fig. 13.15). Tetrahydroxanthones are the monomeric components of interesting mycotoxins such as the beticolins (1063-1070) and the secalonic acids (1034-1046) (see Sect. 13.5.3). 

In 2008, the long-anticipated but never-before-detected monomeric components of the secalonic acids (blennolides and hemisecalonic acids 895 to 900, Fig. 13.9) were isolated from an endophytic Blennoria sp., in addition to secalonic acid B (1037) (vide infra) (Fig. 13.9) and several other biosynthetically related isolates, named blennolides A-G (895-901) (633). The structure of blennolide A (895), the monomeric unit of secalonic acid B (1037), was confirmed using single-crystal X-ray analysis blennolide B (896) is the monomeric unit of secalonic acid D (1035). The configurations of all these compounds were ascertained using CD spectra to determine the absolute stereochemistiy of the 10a position as (R), and... 

Diversonol (932) was selected as a target by the Erase group in their ongoing studies on the synthesis of the secalonic acids (1034-1046) and related natural products 556,560-566), and the successful synthesis of the racemate was reported in 2006 643). The synthesis started with the synthetic intermediate 270 (Scheme 13.13), common with the group s synthesis of blennolide C (897) (see Scheme 13.9). Enone substrate 270 was doubly activated for diastereoselective... 

The secalonic acids (1034—1046) (Fig. 13.27) are comprised of dimers of the blennolides (vide supra). This class of compounds, also named ergochromes, has been the subject to extensive investigation due to their biological activity. 

A novel ergochrome, neosartorin (1078, Fig. 13.33), was isolated from the mycelium of the soil mold Neosartorya fischeri, and the chemical structure was deduced with a variety of spectroscopic techniques (687). This compound is an isomer of the eumitrins. It was determined that the relative configurations at the C-5, -6 and -10 (and C-5, -6 and -10 ) positions are the same as in secalonic acids A and D. 

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