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Total Synthesis of Korormicin
Author(s) -
Kobayashi Yuichi,
Yoshida Shinya,
Nakayama Yuji
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200105)2001:10<1873::aid-ejoc1873>3.0.co;2-o
Subject(s) - chemistry , diastereomer , dihydroxylation , total synthesis , enantiomer , kinetic resolution , lactone , stereochemistry , enantioselective synthesis , chiral auxiliary , catalysis , organic chemistry
Recently, we have assigned the (5 S ,3′ R ,9′ S ,10′ R ) stereochemistry to planar korormicin ( 1 ) on the basis of the specific rotations of the four possible diastereoisomers [i.e., (5 S ,3′ R ,9′ S ,10′ R ), (5 S ,3′ S ,9′ S ,10′ R ), (5 S ,3′ S ,9′ R ,10′ S ), and (5 S ,3′ R ,9′ R ,10′ S ) isomers], which were prepared by a total synthesis. In this article, we describe the synthetic aspects in detail. The intermediates in the synthesis are enamino lactone (5 S )‐ 4 and both enantiomers of acid 5 and of boronate ester 7 . Lactone (5 S )‐ 4 and boronate 7 with (9′ S ,10′ R ) and (9′ R ,10′ S ) chiralities were prepared through asymmetric dihydroxylation of olefins 11 and 30 , respectively, with AD‐mix‐α or ‐β. Compounds (3′ R )‐ and (3′ S )‐ 5 were prepared by kinetic resolution of rac ‐ 19 with asymmetric epoxidation. Condensation of (5 S )‐ 4 and (3′ R )‐ or (3′ S )‐ 5 with DCC in the presence of DMAP and PPTS furnished the advanced intermediate 6 with (5 S ,3′ R ) and (5 S ,3′ S ) chiralities in good yields. Addition of PPTS was important to prevent formation of acyl urea 24 . A nickel‐catalyzed coupling reaction between 6 and 8 [prepared in situ from (9′ S ,10′ R )‐ or (9′ R ,10′ S )‐ 7 and MeLi] produced 9 , which upon deprotection with Bu 4 NF furnished the four diastereoisomers of korormicin ( 1 ).