Pergamon Tetrahedron: Asymmetry 10 (1999) 3547–3557 Enantioselective synthesis of each stereoisomer of the pyranoid linalool oxides: the linalool route Giovanni Vidari, a,* Anna Di Rosa, a Giuseppe Zanoni a and Carlo Bicchi b a Dipartimento di Chimica Organica, Università di Pavia, Via Taramelli 10, 27100 Pavia, Italy b Dipartimento di Scienza e Tecnologia del Farmaco, ViaGiuria 9, 10125 Torino, Italy Received 28 July 1999; accepted 13 August 1999 Abstract Each of the four enantiomerically pure tetrahydropyran linalool oxides was prepared by separate enantioselective Sharpless dihydroxylation of (R)- or (S)-linalyl acetate with AD-mix-α or AD-mix-β, followed by a completely stereoselective N-phenylselenophthalimide cyclization of an intermediate allylic alcohol. © 1999 Elsevier Science Ltd. All rights reserved. 1. Introduction A 2,2,6,6-tetrasubstituted pyran ring is an important structural fragment of many oxygenated natural products and constitutes the basic skeleton of the four pyranoid linalool oxides 1 (3R,6R), 2 (3S,6R), 3 (3R,6S) and 4 (3S,6S). The latter compounds, as different mixtures of stereoisomers, have been found as constituents of many tea, flower and fruit aromas, such as grapes and Carica papaya fruits. 1,2 Even though compounds 1–4 are usually minor constituents of these fragrances, they are considered to be important contributors to a particular ‘note’ or ‘character’ of the scent. 3 However, to our knowledge, nobody has yet described the distinctive odour of each stereoisomer. In addition, they seem to have a strong biological significance in certain pollination systems, acting as insect attractants. 3 Recently, numerous syntheses of linalool oxides have been published, describing valuable selective methods of the construction of substituted pyran rings which were later employed in the synthesis * Corresponding author. Tel: 0039 0382 507322; fax: 0039 0382 507323; e-mail: vidari@chifis.unipv.it 0957-4166/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S0957-4166(99)00359-6 tetasy 3001 Article