Methods for a stereoselective preparation of compounds of type 2b, a key intermediate of a previous synthesis of the tetracyclic diterpene stemarin (1a), have been tested on model compounds 5a, 5c, and 8a. Thus, (+/-)-(1RS,6SR,8SR,11RS)-11-hydroxytricyclo[6.2.2.0(1,6)]dodecan-9-one (5a) was transformed by the Mitsunobu reaction into (+/-)-(1RS,6SR,8SR,11SR)-11-(benzoyloxy)tricyclo[6.2.2.0(1,6)]dodecan-9- one (6b; Scheme 2). The latter was also obtained from (+/-)-(1RS,6SR,8SR,11RS)-11-[(4-toluenesulfonyloxy]tricyclo[6.2.2.0(1,6) ]dodecan-9-one (5c) by the action of Et4N (PhCOO) in acetone. Compound 6b was then converted into (+/-)-(1RS,6RS,8RS,9RS)-tricyclo[6.2.2.0(1,6)]dodecan-9-ol (8b), a model for 2b. Compound 8b was also prepared from its epimer 8a by the Mitsunobu reaction via ester 7b. The inversion of configuration of bicyclo[2.2.2]octan-2-ols or derivates was not previously described. The model studies paved the way to the diastereoselective synthesis of (+)-18-deoxystemarin (1b) via 12-beta-hydroxy-13-methyl-9-beta,13-beta-ethano-9-beta-podocarpan-15-one (10a) and 13-methyl-9-beta,13-beta-ethano-9-beta-podocarpan-12-alpha-ol (11b).

STUDIES FOR A DIASTEREOSELECTIVE SYNTHESIS OF THE TETRACYCLIC DITERPENIC DIOL STEMARIN - A MODEL STUDY FOR A NEW PREPARATION OF THE KEY INTERMEDIATE AND THE SYNTHESIS OF (+)-18-DEOXYSTEMARIN / M. BERETTONI, R. BETTOLO, V. MONTANARI, T. PRENCIPE, S. ROMEO. - In: HELVETICA CHIMICA ACTA. - ISSN 0018-019X. - 74:8(1991), pp. 1671-1678. [10.1002/hlca.19910740807]

STUDIES FOR A DIASTEREOSELECTIVE SYNTHESIS OF THE TETRACYCLIC DITERPENIC DIOL STEMARIN - A MODEL STUDY FOR A NEW PREPARATION OF THE KEY INTERMEDIATE AND THE SYNTHESIS OF (+)-18-DEOXYSTEMARIN

S. ROMEO
Ultimo
1991

Abstract

Methods for a stereoselective preparation of compounds of type 2b, a key intermediate of a previous synthesis of the tetracyclic diterpene stemarin (1a), have been tested on model compounds 5a, 5c, and 8a. Thus, (+/-)-(1RS,6SR,8SR,11RS)-11-hydroxytricyclo[6.2.2.0(1,6)]dodecan-9-one (5a) was transformed by the Mitsunobu reaction into (+/-)-(1RS,6SR,8SR,11SR)-11-(benzoyloxy)tricyclo[6.2.2.0(1,6)]dodecan-9- one (6b; Scheme 2). The latter was also obtained from (+/-)-(1RS,6SR,8SR,11RS)-11-[(4-toluenesulfonyloxy]tricyclo[6.2.2.0(1,6) ]dodecan-9-one (5c) by the action of Et4N (PhCOO) in acetone. Compound 6b was then converted into (+/-)-(1RS,6RS,8RS,9RS)-tricyclo[6.2.2.0(1,6)]dodecan-9-ol (8b), a model for 2b. Compound 8b was also prepared from its epimer 8a by the Mitsunobu reaction via ester 7b. The inversion of configuration of bicyclo[2.2.2]octan-2-ols or derivates was not previously described. The model studies paved the way to the diastereoselective synthesis of (+)-18-deoxystemarin (1b) via 12-beta-hydroxy-13-methyl-9-beta,13-beta-ethano-9-beta-podocarpan-15-one (10a) and 13-methyl-9-beta,13-beta-ethano-9-beta-podocarpan-12-alpha-ol (11b).
Settore CHIM/08 - Chimica Farmaceutica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/185101
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