Oxidation, Baeyer-Villiger Jones

TBS-Protected D-lactaldehyde 961 is used as the chiral source for the synthesis of jS-lactam 969, a key intermediate in the synthesis of the antibiotic monobactam Aztreonam [254] (Scheme 131). The cmcial step in the synthesis, the reaction of A/-trimethylsilylimine 962 with the lithium enolate of STABASE (963), affords ra 5-j5-lactam 964 with 98% diaster-eoselectivity. Desilylation, Jones oxidation, and Baeyer—Villiger oxidation provides acetoxy jS-lactam 968, which in itself is a useful intermediate for the preparation of j5-lactam anti-... 

Treatment of crude (-)-83 with Me3Si0S02CF3 in CH2CI2 (0 °C), followed by acetylation (Ac20/pyridine, 25 °C) and recrystalHzation from EtOAc furnishes the diastereomerically pure naphthacenyl methyl ketone (-)-85 (55%). Baeyer-Villiger oxidation with Se02 and H2O2 leads to (-)-86 (94%), which upon oxidation (4 N Jones-reagent, acetone, 0-20 °C) and saponification (1 N NaOH/THF, 20 °C) affords (-)-87 in 80% yield, a known precursor of (-)-7-deoxyidarubicinone [240,241]. 

Ha and Hart [78] introduced a new functional group conversion of the 4-styryl group in azetidinones of type 142 (Scheme 24). Namely, the trans isomer of 142, readily available from the lithium enolate 147 and the imine 141, was iV-deprotected and the resulting N-H azetidinone converted to the bromohy-drin 148. Dehalogenation and further Jones oxidation of the resulting diastereomeric alcohols 149 produced the ketone 150, which was transformed into the 4-acetic acid derivative 151 by Baeyer-Villiger oxidation. 

A British team [22] subjected the norbomene system (11a) to cleavage by reductive ozonolysis, affording the dialdehyde (12a) which has all the correct stereochemical features required in the prostaglandin. The dialdehyde (12a) was then converted by the sequence — reaction with methyl lithium, Jones oxidation and Baeyer—Villiger oxidation — to the diacetoxy compound (12b) and the latter, after debenzylation, subjected to an acetate rearrangement by refluxing in... 

Peel and Sutherland [34] synthesized the lactone acid (21) starting with the formation of the epimeric diformates by a Prins reaction of norbornadiene and paraformaldehyde to give (22a). Hydrolysis and Jones oxidation of (22a) then gave the keto acid (22b) which underwent ring opening with hydrogen bromide in acetic acid to the bromo compound (23). Baeyer-Villiger oxidation of the latter and addition of sulphuric acid to the reaction mixture followed by work up with alkali afforded an overall conversion to (21) of which the p-bromo-phenacyi ester was converted by the sequence - p-phenylbenzoylation, reduction with zinc and acetic acid and diborane reduction - to the alcohol (14d), previously taken forward to the aldehyde (lb) by Corey. 

The synthesis of PS-5 was achieved by treatment of silylimine of 0-protected (S) lactic aldehyde with the lithium enolate of /-butyl butanoate. The reaction is highly diastereoselective affording almost completely the trans a2etidinone with the natural configuration at C3. This azetidinone was converted, by sequential Jones and Baeyer-Villiger oxidation of hydroxyethyl side chain to the 4-acetoxy doivative that represents a most useful chiral building block fcv the synthesis of final carbapenem PS-5 via the Merck procedure (Scheme 8). 

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