- Asymmetric Synthesis of (?)-Dictyopterene C' and its Derivatives via Catalytic Enantioselective Cyclopropanation
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An efficient and simple method for enantioselective synthesis of (?)-dictyopterene C' and its derivatives was developed on the basis of chiral oxazaborolidinium ion-catalyzed enantioselective cyclopropanation and divinylcyclopropane-cycloheptadiene rearra
- Kim, Taehyeong,Kim, Jae Yeon,Park, Kyung Yee,Ryu, Do Hyun
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- Pericyclic reactions in nature: Synthesis and Cope rearrangement of thermolabile bis-alkenylcyclopropanes from female gametes of marine brown algae (Phaeophyceae)
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The biosyntheses of the 6-substituted cyclohepta-1,4-dienes dictyotene (1), ectocarpene (2), desmarestene (3), vinylcycloheptadiene (4) and lamoxirene (5) involve a spontaneous Cope rearrangement of thermolabile bis-alkenylcyclopropane precursors like 16,
- Pohnert, Georg,Boland, Wilhelm
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p. 13681 - 13694
(2007/10/03)
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- ENZYMATIC HYDROLYSIS OF CYCLOPROPANES. TOTAL SYNTHESIS OF OPTICALLY PURE DICTYOPTERENES A AND C'.
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Enzymatic hydrolysis of cis-1,2-bis(butyryloxymethyl)cyclopropane 3 under optimized conditions gives, in quantitative yield, optically pure cis-(1S,2R)-1-hydroxymethyl-2-butyryloxymethylcyclopropane 1.This compound is a versatile cyclopropane synthon as exemplified by the total synthesis of optically pure seaweed pheromones Dictyopterenes A and C'.
- Grandjean, D.,Pale, P.,Chuche, J.
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p. 1215 - 1230
(2007/10/02)
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- Diastereoselective cyclopropanations of chiral bicyclic lactams leading to enantiomerically pure cyclopropanes. Application to the total synthesis of CIS-(1S, 3R)-deltamethrinic acid and R-(-)- dictyopterene C
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A novel diastereoselective cyclopropanation based on readily available chiral bicylic lactams (1b-c, 6a-b) has provided a number of enantiomerically pure cyclopropanes. Cyclopropanations of unsaturated lactams (10a-h, 12-14) were performed using sulfur ylides as well as a 3+2 cycloaddition-photolysis sequence and furnished the desired cyclopropane adducts (16, 17, 19, 22) in fair to excellent yields. In all cases involving sulfur ylides, cyclopropanations proceeded with a high degree of exo/endo diastereoselectivity (>;90%). However, the mode of addition, exo vs endo, was found to be highly dependent on the angular substituent of the unsaturated lactam. In the case of diazoalkane cycloadditions, high regioselectivity was observed in all cases although exo/endo selectivity was governed by the diazoalkane employed. Diazoisopropane, being more reactive than diazomethane, normally led to lower diastereomeric ratios. Minor diastereomers could be readily removed by chromatography or in most cases by a single recrystallization to provide diastereomerically pure cyclopropyl bicyclic lactams (16, 17, 19, 22). Applications of this methodology to compounds of biological significance was exemplified by an asymmetric, total synthesis of cis-(1S, 3R)-deltamethrinic acid (34) and R-(-)- dictyopterene C′ (42) in high enantiomeric purity.
- Romo, Daniel,Romine, Jeffrey L.,Midura, Wanda,Meyers
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p. 4951 - 4994
(2007/10/02)
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- ENANTIOSELECTIVE SYNTHESIS OF DICTYOPTERENE C 6R-(-)-BUTYL-2,5-CYCLOHEPTADIENE THE PHEROMONE OF SEVERAL DICTYOTALES (PHAEOPHYCEAE)
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R-(-)-Dictyopterene C (1) is a widespread constituent of many marine brown algae (Phaeophyceae).A highly enantioselective synthesis of 1 and its enantiomer ent-1 via chromatographic separation of the diastereomeric γ-hydroxyphenylethylamide intermediates 3a and 3b is described.
- Schotten, Theo,Boland, Wilhelm,Jaenicke, Lothar
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p. 2349 - 2352
(2007/10/02)
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