Pikronolide synthesis

The additional presence of a 3-methoxy substituent on the benzyl group confers greater stability on the intermediate cation, and consequently oxidation of DMPM ethers by DDQ is even more facile. Yonemitsu and cowoikers have used this differential reactivity of substituted benzyl ethers to great effect in the total synthesis of the macrolide antibiotics methynolide, tylonolide, (95)-9-dihydroerythro-nolide and pikronolide. The pikronolide synthesis provides an excellent example of the selective, sequential deprotection of DMPM, MPM and benzyl ether protecting groups (Scheme 7). 

Yonemitsu s pikronolide synthesis is based on the coupling of the C -Ciq (123) and C11-C13 (30) segments derived from D-glucose, and the effective application of benzyl type protecting groups, MPM (4-methoxybenzyl) and DMPM (3,4-dimethoxybenzyl), which were developed by his group for the macrolide synthesis. 

Chakraborty, T. K. Das, S. Synthesis of chiral 1,3-diols by radical-mediated regioselective opening of 2,3-epoxy alcohols using Cp2TiCl2. Tetrahedron Lett. 2002, 43, 2313-2315. Nakajima, N. Tanaka, T. Hamada, T. Oikawa, Y. Yonemitsu, O. Highly stereoselective total synthesis of pikronolide, the aglycon of the... 

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