67 光学活性カルバペネム鍵合成中間体の合成研究(口頭発表の部)

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The carbapenem antibiotics represented by 1, 2, and 3, have been the focus of current synthetic endeavor due to their potent antibacterial activities and broad spectra. We wish to report here novel and efficient synthetic routes to the optically active carbapenem key intermediates 4, 5, and 6. Thus, it was found that the [2+2]-cycloaddition reaction of the chiral aliphatic imine 9 prepared from (S)-7, could proceed in a highly stereoselective manner to afford the 3,4-trans-β-lactam 10 as a major product (Scheme II). The β-lactam (10) was readily elaborated to 5 (Scheme III). The similar methodology could be applied to the syntheses of the other key intermediates 4 and 6. Thus, the addition reaction of diketene to the chiral imine prepared from (S)-13, was found to produce 17 in a highly stereoselective manner (Scheme IV). 6 and 4 could be readily prepared from 17 (Scheme V and VI). Taking into account high stereoselectivity in the β-lactam formation and uses of commercially available inexpensive (S)-7 and (S)-13 as starting materials, the overall processes may hold promise as the practical synthetic methods of 5 and 6. As the second method for preparing 5, the Reformatsky reaction of 6 was studied. It was found that the reactions of sterically crowded achiral 2-oxazolidone derivatives (24b,f)in the presence of zinc dust in refluxing THF gave rise to 25β as major products (at most, 95:5) in excellent yield (Scheme VII). Trans-formation of 25β to 5 could be successfully accomplished (Scheme VIII). This latter process is also anticipated to be one of the most practical synthetic methods of 5 because of high β-diastereoselectivity, high overall yield, mild reaction conditions, and use of inexpensive reagents.
天然有機化合物討論会の論文
1988-09-26

67 光学活性カルバペネム鍵合成中間体の合成研究(口頭発表の部)

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