TETRAHEDRON LETTERS Tetrahedron Letters 42 (2001) 21 – 24 Pergamon Oxidative cleavage of unsaturated 1,2-diols using chiral lead-tetracarboxylates obtained by in situ metathesis Jose ´ Ignacio Candela Lena, O  zge Sesenoglu, Nicolas Birlirakis and Sime ´on Arseniyadis* Institut de Chimie des Substances Naturelles, CNRS, F -91198 Gif -sur -Yvette, France Received 16 October 2000; accepted 25 October 2000 Abstract —A combination of an acetate metathesis/cascade transformations process, providing ring enlarged systems decorated with a chiral auxiliary, is presented. The use of a chiral carboxylic acid, such as (S )-2-acetoxypropionic acid, gives diastereomeric mixtures when performed in the racemic series, offering the possibility of a chemical resolution. © 2000 Published by Elsevier Science Ltd. While designing strategies for the taxoid diterpene skeleton construction, a serendipitous discovery led to the development of a new ‘cascade-type’ ring-expan- sion/rearrangement methodology. 1 The utility of this methodology with regard to the synthesis of biologi- cally active natural products was demonstrated by the large scale preparation of a conveniently functionalized taxoid C-ring precursor 2 which in turn was elaborated into the highly oxygenated taxoid ABC tricyclic sys- tem. 3 Exploring the solvent effect on the above men- tioned transformations, mediated by Pb(OAc) 4 , we examined a number of solvents compatible with the reagent used, namely benzene, trifluorotoluene, ace- tone, methylene chloride, chloroform, DME, DMF, THF and acetic acid. The product ratios and reaction rates were clearly dependent on solvent polarity and the observed solvent effect on the rate of cascade transfor- mations can be rationalized by examining the proposed mechanism of this reaction sequence. 4 In this communi- cation, we report examples of this methodology carried out in a chiral carboxylic solvent, ensuring high com- plexity but also enantiomeric purity in a single synthetic operation. During a preliminary study 5 we noticed that the use of deuterium labeled acetic acid led to the Scheme 1. (a) Pb(OAc) 4 , CD 3 COOD, rt. (b) Pb(OAc) 4 ,(S )-2-acetoxypropionic acid, rt. Keywords : ring expansion; cascade transformations; acetate metathesis; chiral carboxylic solvents. * Corresponding author. Fax: 33-1-69.07.72.47; e-mail: simeon.arseniyadis@icsn.cnrs-gif.fr 0040-4039/01/$ - see front matter © 2000 Published by Elsevier Science Ltd. PII:S0040-4039(00)01887-6