19 簡單な天然有機化合物の簡單な合成III
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概要
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It is curious that the question of "how to design the simplest synthesis of a given molecule" is hitherto much ignored in spite of its apparent gravity in organic synthetic chemistry. In this connection, the present authors have shown a simple methodology about the logic of synthesis which has been demonstrated by the two or three step synthesis of four different series of alkaloids having an interesting skeletal structure in these two years. This paper adds two more examples of the synthesis on these lines. (I) One step synthesis of halfordinol (2a) A comprehensive study of an imaginative bond disconnection of oxazole ring system aids the synthesis of halfordinol while a new one step synthesis of 2,5-disubstituted oxazole has also been developed through these consideration. Thus halfordinol (2a) is obtained in one step by the reaction of p-hydroxymandelonitril (3) with nicotinaldehyde in the presence of SOCl_2 and HCl. (II) Two step synthesis of dl-elaeocarpine (4) and dl-isoelaeocarpine (5) Upon the consideration of the hypothetical mechanism of reaction course, a new reductive condensation of dihydropyridines with salicylaldehydes is developed. Thus dihydroindolizinium salt 16 readily reacts with 6-methylsalicylaldehyde (17) in the presence of LiAlH_4 to give a reductive condensation product 18. Oxidation and cyclization of 18 by Jones' reagent completes the two step synthesis of dl-elaeocarpine (4) and dl-isoelaeocarpine (5).
- 天然有機化合物討論会の論文
- 1970-10-01