Flexible and Simple Route for the Stereoselective Synthesis of Trisubstituted γ-Butyrolactones: Total Synthesis of (+)-Blastomycinone and its Analogs
作者:Palakodety Radha Krishna、V. V. Reddy、G. V. Sharma
DOI:10.1055/s-2004-829173
日期:——
A flexible route for the stereoselectivesynthesis of trisubstituted γ-butyrolactones, namely (+)-blastomycinone and its analogs, is devised by the Sharpless asymmetric epoxidation and the regioselective ring opening reaction with dibutylcopper lithium as the key steps to introduce the requisite alkyl chain.
The intramolecular nitrile oxide cycloaddition reaction on chiral (E) and (Z) olefins featuring a sulphuratom along the carbon chain connecting dipole and dipolarophile occurs with poor to excellent anti stereoselectivity, which is mainly affected by the substitutents at the allylic stereocenter. The possibility of converting the cycloadducts into stereoisomerically pure β-ketols has been established
The diastereoselective approach to enantiomerically pure furyl hydroperoxides of general type 1 has been accomplished starting from (S)-(-)-ethyl lactate. In the first part of the synthesis the alkylating reagents 7a,b were efficiently produced to be used in the second part for a 4-step known methodology to obtain furyl hydroperoxides. The most relevant transformation of the synthesis is the first reported diastereoselective iodoenoletherification of 2-acetyl-4-heptenoate esters 8a,b possessing a phi-chiral center. Furthermore, the final radical oxidation performed on (E)-5-alkylidene-4,5-dihydrofurans 11a,b led to formation of hydroperoxides (S,S)-12a,b in a diastereocontrolled manner due to 1,2-asymmetric induction. (C) 1999 Elsevier Science Ltd. All rights reserved.
YAMAMOTO YOSHINORI; NISHII SHINJI; IBUKA TOSHIRO, J. CHEM. SOC. CHEM. COMMUN.,(1987) N 6, 464-466