81 二環式化合物の触媒的不斉合成 : カプネラン合成中間体への応用(口頭発表の部)

概要

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A catalytic asymmetric C-C bond-forming reaction by the use of a Heck-type reaction has been realized for the first time, giving the cis-decalin derivative 2 and the bicyclo[3.3.0]octane derivative 17 in an optically active form. Treatment of the prochiral alkenyl iodide 1 (R=CH_2OTBDMS) with Cl_2Pd(R)-BINAP (10 mol%), Ag_3PO_4 (2 molar equiv) and CaCO_3 (2.2 molar equiv) in NMP (1-methyl-2-pyrrolidinone) at 60℃ for 84 h provided the cis-decalin derivative 2 in 80% ee (67% yield). As shown in Table 4, an important role of silver salts in an asymmetric Heck-type reaction was also demonstrated. Assignment of the absolute configuration was achieved by application of the CD exciton chirality method to 5. The cyclized product 2 (R=COOMe) has been found to be readily converted to the highly functionalized compound 6. Furthermore, the optically active bicyclo[3.3.0]octane derivative 17 was also synthesized by the use of an asymmetric Heck-type reaction. That is, treatment of 12 with [Pd(allyl)Cl]_2 (10 mol %), (S,S)-Chiraphos (10 mol %), Bu_4NOAc (2.9 molar equiv) and AgOAc (1.1 molar equiv) in toluene at 60℃ for 161 h afford 17 in 25% ee (54% yield). The bicyclo[3.3.0]octane derivative 17 was transformed into 10 via a three-step sequence of reactions, which is a key intermediate for the synthesis of capnellenetriol 11 (R=Me) and capnellenetetraol 11 (R=CH_2OH). Further studies along this line are in progress.
1990-09-25