75(P60) 2,4,4,6-Tetrabromo-2,5-cyclohexadienone/PPh_3から生成する新規反応剤を用いた種々の官能基合成と生理活性天然物合成への応用(ポスター発表の部)

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In the course of the work on brominative cyclization of polyenes, we found that treatment of 2,4,4,6-tetrabromo-2,5-cyclohexadienone with PPh_3 led to stable phosphonium salt (A) and this salt was quite effective for various functional group preparation. We now report the preparation of alkyl bromides from alcohols, THP ethers and silyl ethers, ester synthesis, and azide formation from alcohols using salt (A). We also describe the application of this method to the synthesis of biologically active natural products. 1. Preparation of alkyl bromides from alcohols and THP ethers Reaction of alcohols and THP ethers with (A) in CH_2Cl_2 or CH_3CN led to alkyl bromides in excellent yields. This reagent gave also satisfactory results for secondary alcohols and THP ethers. 2. Preparation of alkyl bromides from silyl ethers This reagent can be also employed for the bromide formation from sterically less hindered silyl ethers (TMS, TES, TBDMS).3. Preparation of esters from alcohols and carboxylic acids Treatment of alcohols and carboxylic acids with this salt (A) in CH_3NO_2 provided esters in moderate yields. 4. Preparation of formates from alcohols This reagent gave formates from alcohols in DMF in the presence of ZnX_2(X=Br for primary alcohols, I for secondary alcohols) in high yields. 5. Preparation of azides from alcohols Treatment of alcohols with (A) in the presence of Zn(N_3)_2・2Py led to azides in excellent yields. CH_3CN/toluene, CH_3CN/toluene/THPA or THE was the best solvent system. In particular, in the case of allylic and propargylic alcohols, the reaction proceeded very rapidly, allowing only allylic and propargylic positions to be azidated in the presence of saturated alcohols. 6. Application of this method to natural product synthesis a)Synthetic study of Blasticidin S-related compounds Blasticidin S is a powerful agent against rice blast disease. In association with the work on structure-activity relationship, we tried the synthesis of two related compounds using our developed reagent. b)Synthetic Study of AZT 3'-Azido-3'-deoxythymidine(AZT) is one of the most useful drugs against AIDS. A synthetic approach from thymidine via anhydrothymidine was examined.
天然有機化合物討論会の論文
1997-07-20

75(P60) 2,4,4,6-Tetrabromo-2,5-cyclohexadienone/PPh_3から生成する新規反応剤を用いた種々の官能基合成と生理活性天然物合成への応用(ポスター発表の部)

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