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Selective Synthesis of 5,6‐Disubstituted 3‐Methyl‐2(2 H )‐pyranones and 6‐Substituted 3‐Methyl‐2(2 H )‐pyranones, Including Fusalanipyrone and Gibepyrone A
Author(s) -
Biagetti Matteo,
Bellina Fabio,
Carpita Adriano,
Viel Stéphane,
Mannina Luisa,
Rossi Renzo
Publication year - 2002
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 - 10.1002/1099-0690(200203)2002:6<1063::aid-ejoc1063>3.0.co;2-m
Subject(s) - chemistry , organic chemistry , natural product , methyl formate , medicinal chemistry , catalysis
The 6‐substituted 3‐bromo‐5‐iodo‐2(2 H )‐pyranones 11 , prepared by iodolactonization of the corresponding 5‐substituted ( E )‐2‐bromo‐2‐en‐4‐ynoic acids 10 , were used as precursors to 5,6‐disubstituted 3‐methyl‐2(2 H )‐pyranones 8 and 6‐substituted 3‐methyl‐2(2 H )‐pyranones 7 . The synthesis of compounds 8 involved two consecutive Stille‐type reactions, whereas the approach followed to prepare compounds 7 consisted of the selective reduction of the dihalogen derivatives 11 to the corresponding 6‐substituted 3‐bromo‐2(2 H )‐pyranones 12 , followed by a Pd/Cu‐catalysed reaction with tetramethyltin. However, this synthetic approach to compounds 7 proved to be unsuitable for preparing stereoisomerically pure fusalanipyrone ( 7a ), a natural product isolated from Fusarium solani . Nevertheless, 7a and gibepyrone A ( 7b ), which is a natural product isolated from Gibberella fujikuroi , could be synthesized in stereoisomerically pure form by reaction sequences involving iodolactonization of easily available (2 Z ,6 Z )‐ and (2 Z ,6 E )‐2,6‐dimethyl‐2,6‐octadien‐4‐ynoic acids ( 16a ) and ( 16b ), respectively, followed by Pd‐catalysed triethylammonium formate reduction of the thus obtained 6‐substituted 5‐iodo‐3‐methyl‐2(2 H )‐pyranones 17a and 17b , respectively. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)