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Synthesis of Xyloketals, Natural Products from the Mangrove Fungus Xylaria sp
Author(s) -
Krohn Karsten,
Riaz Muhammad,
Flörke Ulrich
Publication year - 2004
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200300629
Subject(s) - chemistry , phloroglucinol , enone , furan , stereochemistry , tris , adduct , steric effects , ring (chemistry) , medicinal chemistry , organic chemistry , biochemistry
The xyloketal family of compounds was synthesized by condensation of phloroglucinol ( 7 ) or 2,4‐dihydroxyacetophenone ( 15 ) with the enone 8a or 14 in multistep, one‐pot, domino reactions, leading to the xyloketals and 5‐demethylxyloketals, respectively. In the case of condensation with phloroglucinol ( 7 ), the mono‐, bis, and tris adducts 6 / 18 , 2 / 19 , 1 / 20 are formed; their ratios depend on the ratio of stating materials and reaction time. The ring junction of the pyran and furan rings B and C (at C‐2 and C‐6) is always cis . The cis orientation of the methyl groups at C‐2 and C‐5 is also predominant (8.5:1.5), as found in the natural products. In the bis and tris adducts ( 2 / 19 , 1 / 20 ), the relative orientation of the rings B and C can be syn and anti , with the sterically less demanding anti orientation slightly favored statistically. Xyloketal D ( 4a ) was obtained in the condensation of 15 with enantiomerically enriched enone 8a , confirming the absolute configuration of the natural product. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)