Substrate-Directed Diastereoselective Hydroformylation: Key Step for the Assembly of Polypropionate Subunits

✍ Scribed by Bernhard Breit; Mario Dauber; Klaus Harms

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 181 KB
• Volume: 5
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/(sici)1521-3765(19991001)5:10<2819::aid-chem2819>3.0.co;2-z

✦ Synopsis

Stereoselective hydroformylation of methallylic alcohols of types 3 and 4, that employed the substratebound catalyst-directing ortho-diphenylphosphanylbenzoyl (o-DPPB) group, was used as a key step for the construction of bifunctionalized stereotriads, which are central building blocks of polyketide natural products. The required diastereomerically pure syn-and anti-starting methallylic alcohol systems 3 and 4 were obtained either by Cramselective carbonyl reduction, Fra  ter alkylation, or by chelation-controlled carbonyl reduction. Enantiomerically pure stereotriad building blocks were derived from a combination of an Evans aldol addition and subsequent o-DPPB-directed stereoselective hydroformylation (324). A crystal structure analysis for steretriad building block 24 confirmed the relative and absolute configuration of the stereogenic centers. Additionally, it provided evidence for a previously postulated preferred conformation of the catalyst-directing o-DPPB group as well as of the polyketide main chain.