Synthesis 2005(16): 2798-2809  
DOI: 10.1055/s-2005-918404
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart · New York

Design, Synthesis and Olfactory Properties of 2-Substituted 2-tert-Butyl-5-­methyl-2,5-dihydrofurans: seco-Derivatives of Theaspiranes

Philip Kraft*, Kasim Popaj, Agnese Abate
Givaudan Schweiz AG, Fragrance Research, Überlandstrasse 138, 8600 Dübendorf, Switzerland
Fax: +41(44)8242926; e-Mail: philip.kraft@givaudan.com;
Further Information

Publication History

Received 2 July 2005
Publication Date:
23 September 2005 (online)

Abstract

Two seco-theaspiranes with pronounced blackcurrant notes, 2-tert-butyl-5-methyl-2-propyl-2,5-dihydrofuran (7) and 2-tert-butyl-5-methyl-2-propyltetrahydrofuran (8), were synthesized by a synthetic sequence consisting of Grignard reaction, Lindlar ­hydrogenation, and cyclization followed by optional Pd-catalyzed hydrogenation. The sequence was modified for the synthesis of the oxygenated analogs 2-(2′-tert-butyl-5′-methyltetrahydrofuran-2′-yl)propan-2-ol (9) and 3-(2′-tert-butyl-5′-methyltetrahydrofuran-2′-yl)butan-2-one (10). The first modification featured trimethyl­silyl ether protection and stepwise construction of the alkyne moiety necessitated by steric hindrance. In the second modification, a but-2-en-2-yl group was utilized as latent 3-hydroxybut-1-en-2-yl functionality, and the steric constraint around the tertiary hydroxy group was exploited to introduce a stereocenter by SN2 ring closure. As for the parent compounds 7 and 9, the odor of the oxygenated seco-­theaspiranes was shifted towards a woody tonality. The like-diastereo­mer 9a even had a typical patchouli profile, and the ­enantiomers 10a and 10b differed significantly in their olfactory properties.

1

The synthesis of 10a/b is part of the projected Ph.D. Thesis of Agnese Abate, Dipartimento di Chimica, Materiali ed Ingegneria Chimica del Politecnico di Milano.