A short enantiospecific route to isodaucane sesquiterpenes from limonene. On the absolute configuration of (+)-aphanamol I and II.
摘要:
The isodaucane sesquiterpenes (+)-aphanamol I (3) and (-)-2-oxoisodauc-5-en-12-al [(-)-6] have been prepared in a short reaction sequence from 5(S)-isopropyl-2-methyl-l-cyclopentene-1-carbaldehyde (S)-23 (readily obtainable from (+)-limonene). Key steps were a de Mayo type photocyclization of an 3-acyloxy-2-cyclopenten-1-one with 3(S)-isopropyl-1-methylcyclopentene [(S)-24] to a [5.3.0.0(2.6)]tricyclodecanone (e.g., (-)-28) with the desired configuration at all stereocenters and the formation of 3 by a base-catalyzed fragmentation of the gamma,delta-epoxyalcohol intermediate 33 (R = H), which produced all the desired functional groups in one step. The stereochemical assignments were supported by CD data as well as by the synthesis of (-)-norbourbonone (29) from (S)-24, which is a novel chiral intermediate. These results are in confliction with some earlier assignmnents of the absolute configuration in the isodaucane group of sesquiterpenes.
A short enantiospecific route to isodaucane sesquiterpenes from limonene. On the absolute configuration of (+)-aphanamol I and II.
摘要:
The isodaucane sesquiterpenes (+)-aphanamol I (3) and (-)-2-oxoisodauc-5-en-12-al [(-)-6] have been prepared in a short reaction sequence from 5(S)-isopropyl-2-methyl-l-cyclopentene-1-carbaldehyde (S)-23 (readily obtainable from (+)-limonene). Key steps were a de Mayo type photocyclization of an 3-acyloxy-2-cyclopenten-1-one with 3(S)-isopropyl-1-methylcyclopentene [(S)-24] to a [5.3.0.0(2.6)]tricyclodecanone (e.g., (-)-28) with the desired configuration at all stereocenters and the formation of 3 by a base-catalyzed fragmentation of the gamma,delta-epoxyalcohol intermediate 33 (R = H), which produced all the desired functional groups in one step. The stereochemical assignments were supported by CD data as well as by the synthesis of (-)-norbourbonone (29) from (S)-24, which is a novel chiral intermediate. These results are in confliction with some earlier assignmnents of the absolute configuration in the isodaucane group of sesquiterpenes.
A short enantiospecific route to isodaucane sesquiterpenes from limonene. On the absolute configuration of (+)-aphanamol I and II.
作者:Thomas Hansson、Boerje Wickberg
DOI:10.1021/jo00046a018
日期:1992.9
The isodaucane sesquiterpenes (+)-aphanamol I (3) and (-)-2-oxoisodauc-5-en-12-al [(-)-6] have been prepared in a short reaction sequence from 5(S)-isopropyl-2-methyl-l-cyclopentene-1-carbaldehyde (S)-23 (readily obtainable from (+)-limonene). Key steps were a de Mayo type photocyclization of an 3-acyloxy-2-cyclopenten-1-one with 3(S)-isopropyl-1-methylcyclopentene [(S)-24] to a [5.3.0.0(2.6)]tricyclodecanone (e.g., (-)-28) with the desired configuration at all stereocenters and the formation of 3 by a base-catalyzed fragmentation of the gamma,delta-epoxyalcohol intermediate 33 (R = H), which produced all the desired functional groups in one step. The stereochemical assignments were supported by CD data as well as by the synthesis of (-)-norbourbonone (29) from (S)-24, which is a novel chiral intermediate. These results are in confliction with some earlier assignmnents of the absolute configuration in the isodaucane group of sesquiterpenes.