Issue in Honor of Dr. Rama Rao ARKIVOC 2005 (iii) 74-82 ISSN 1424-6376 Page 74 © ARKAT USA, Inc Stereoselective synthesis of (-)-pestalotin A. Shashidhar Kumar, Pushpal Bhaket, and B. Venkateswara Rao* Division of Organic Chemistry, Indian Institute of Chemical Technology Hyderabad - 500 007, India E-mail: venky@iict.res.in Dedicated to Dr. A.V. Rama Rao on the occasion of his 70 th birthday (received 16 Jul 04; accepted 05 Nov 04; published on the web 12 Nov 04) Abstract The asymmetric synthesis of (-)-pestalotin is described using OsO 4 -catalyzed asymmetric dihydroxylation and utilization of substituted aromatic system as a masked β-ketoester as the key steps in the reaction sequence. Keywords: Asymmetric dihydroxylation, Birch reduction, ozonolysis Introduction Pestalotin 1, a gibberellin synergist, was first discovered by Kimura et al 1 from a culture broth of Pestalotia Cryptomeriaecola Sawada, which is a fungus pathogenic for the Japanese cedar, Cryptomeria japonica. Later, Ellestad et al 2 also isolated 1 as a minor metabolite from the fermentation culture P880, an unidentified penicillium species and gave the code LLP-880α. The 6-substituted 5,6-dihydro-2-pyrone skeleton in pestalotin 1 which also occurs in many natural products show diverse biological activity 3 . O OH OMe O (-)-Pestalotin 1 The presence of two contiguous stereogenic centers in (-)-pestalotin 1 has made it an attractive synthetic target since its discovery. Several synthesis of racemic 1c,4a-c and optically active forms