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Organometallic enantiomeric scaffolding. A molybdenum-mediated intramolecular nucleophilic ketalization-demetalation cascade. Total synthesis of (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin.

ABSTRACT: TpMo(CO)(2)(5-oxo-eta(3)-pyranyl) scaffolds bearing an internal alkoxide undergo a novel intramolecular nucleophilic ketalization reaction. The anionic intermediate is easily demetalated, rapidly providing the 6,8-dioxabicyclo[3.2.1]oct-3-en-2-one framework in moderate to good yields with high enantiopurity. An enantiocontrolled total synthesis of (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin was accomplished utilizing the reaction sequence.

SUBMITTER: Cheng B

PROVIDER: S-EPMC2736330 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Organometallic enantiomeric scaffolding. A molybdenum-mediated intramolecular nucleophilic ketalization-demetalation cascade. Total synthesis of (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin.

Cheng Bo B Liebeskind Lanny S LS

Organic letters 20090801 16

TpMo(CO)(2)(5-oxo-eta(3)-pyranyl) scaffolds bearing an internal alkoxide undergo a novel intramolecular nucleophilic ketalization reaction. The anionic intermediate is easily demetalated, rapidly providing the 6,8-dioxabicyclo[3.2.1]oct-3-en-2-one framework in moderate to good yields with high enantiopurity. An enantiocontrolled total synthesis of (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin was accomplished utilizing the reaction sequence. ...[more]

PMID: 19627126

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Crystal structure of (1R,2S,4R,7R,8S,9R)-3,3-dichloro-8,9-epoxy-4,8,12,12-tetramethyltricyclo[5.5.0.0(2,4)]dodecane.

Project description:The title compound, C16H24Cl2O, is built up from two fused six- and seven-membered rings which bear a di-chloro-cyclo-propane group and an ep-oxy group, respectively. In the mol-ecule, the six-membered ring adopts an envelope configuration with the C atom linking the ep-oxy ring at the flap, while the seven-membered ring adopts a boat-sofa conformation.

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Sodium (1R,2S,5S)-2-hydr-oxy-6,6-dimethyl-bicyclo-[3.1.1]heptane-2-carboxyl-ate penta-hydrate.

Project description:In the title compound, Na(+)·C(10)H(15)O(3) (-)·5H(2)O, the vertices of a distorted octa-hedron centred on the Na(+) cation are defined by six O atoms of water mol-ecules. The edge-sharing Na(H(2)O)(6) octa-hedra form a chain extended along the b-axis direction with adjacent Na(+) cations related by a twofold screw symmetry operation. The organic anion, which is not in close contact with the Na(+ )cation, is hydrogen-bonded to an uncoordinated water mol-ecule and to water mol-ecules of the Na(H(2)O)(6) octa-hedra.

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Organometallic enantiomeric scaffolding: a strategy for the enantiocontrolled construction of regio- and stereodivergent trisubstituted piperidines from a common precursor.

Project description:Reported herein is a general and efficient method to construct 2,3,6-trisubstituted piperidines in a substituent-independent fashion. From the high enantiopurity organometallic scaffold (-)-Tp(CO)(2)[(?-2,3,4)-(1S,2S)-1-benzyloxycarbonyl-5-oxo-5,6-dihydro-2H-pyridin-2-yl)molybdenum (Tp = hydridotrispyrazolylborato), a variety of TpMo(CO)(2)-based 2,3,6-trifunctionalized complexes of the (?-3,4,5-dihydropyridinyl) ligand were easily obtained in 5 steps through a sequence of highly regio- and stereospecific metal-influenced transformations (15 examples). From the 2,3,6-trifunctionalized molybdenum complexes, either 2,6-cis-3-trans or 2,3,6-cis systems were selectively obtained through the choice of an appropriate stereodivergent demetalation protocol. The potential of this strategy in synthetic chemistry was demonstrated by the short total synthesis of four natural and one non-natural alkaloids: indolizidines (±)-209I and (±)-8-epi-219F in the racemic series, and enantiocontrolled syntheses of (-)-indolizidine 251N, (-)-quinolizidine 251AA, and (-)-dehydroindolizidine 233E.

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(1R,2S,3R,5S)-5-(1H-Benzimidazol-2-yl)cyclo-hexane-1,2,3,5-tetraol mono-hydrate.

Project description:In the crystal structure of the title compound, C(13)H(16)N(2)O(4)·H(2)O, inter-molecular N-H?O, O-H?O and O-H?N hydrogen bonds form an extensive three-dimensional network, consolidating the crystal packing. The cyclo-hexane ring adopts a chair conformation.

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Organometallic enantiomeric scaffolding: general access to 2-substituted oxa- and azabicyclo[3.2.1]octenes via a Bronsted acid catalyzed [5 + 2] cycloaddition reaction.

Project description:6-Substituted TpMo(CO) 2(eta-2,3,4-pyranyl)- and TpMo(CO) 2(eta-2,3,4-pyridinyl) scaffolds (Tp = hydridotrispyrazolylborato) function as reaction partners in an efficient regio- and stereocontrolled synthesis of functionalized oxa- and azabicyclo[3.2.1]octenes through a novel Brønsted acid catalyzed [5 + 2] cycloaddition reaction. Excellent exo-selectivities are obtained, and the reaction gives products with complete retention of enantiomeric purity when carried out with chiral, nonracemic scaffolds. The substituent at C-6 of the eta (3)-coordinated heterocyclic scaffold not only influences [5 + 2] reactivity but also plays a critical role in the demetalation step directing the reaction to only one of two possible products.

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(5S)-3-Chloro-4-diallyl-amino-5-[(1R,2S,5R)-2-isopropyl-5-methyl-cyclo-hex-yloxy]furan-2(5H)-one.

Project description:The title compound, C(20)H(30)ClNO(3), was obtained via a tandem asymmetric Michael addition-elimination reaction of (5S)-3,4-dichloro-5-(l-menth-yloxy)-2(5H)-furan-one and diallyl-amine in the presence of potassium fluoride. The mol-ecular structure contains an approximately planar five-membered furan-one ring [maximum atomic deviation = 0.0221?(3)?Å] and a six-membered ring adopting a chair conformation.

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(5S)-3-Chloro-5-[(1R,2S,5R)-2-isopropyl-5-methyl-cyclo-hex-yloxy]-4-(4-methyl-piperidin-1-yl)furan-2(5H)-one.

Project description:The title compound, C(20)H(32)ClNO(3), was obtained via a tandem asymmetric Michael addition-elimination reaction of (5S)-3,4-dichloro-5-(l-menth-yloxy)furan-2(5H)-one and 4-methyl-piperidine in the presence of potassium fluoride. The furan-one ring is approximately planar [maximum atomic deviation = 0.022 (2) Å] while the cyclo-hexane ring adopts a chair conformation. Weak inter-molecular C-H⋯O hydrogen bonding is present in the crystal structure.

| S-EPMC3051989 | biostudies-literature

(5S)-3-Chloro-4-(2,5-dihydro-1H-pyrrol-1-yl)-5-[(1R,2S,5R)-2-isopropyl-5-methyl-cyclo-hex-yloxy]furan-2(5H)-one.

Project description:The title compound, C(18)H(26)ClNO(3), was obtained via a tandem asymmetric Michael addition-elimination reaction of 3,4-dichloro-5-(S)-(l-menth-yloxy)furan-2(5H)-one and 2,5-di-hydro-1H-pyrrole in the presence of potassium fluoride. In the mol-ecule, the nearly planar dihydro-pyrrole ring [maximum atomic deviation = 0.019?(3)?Å] is oriented at a dihedral angle of 10.73?(8)° to the the nearly planar furan-one ring [maximum atomic deviation = 0.011?(2)?Å]; the cyclo-hexane ring adopts a chair conformation. In the crystal, mol-ecules are linked via weak inter-molecular C-H?O hydrogen bonds, forming supra-molecular chains running along the b axis.

| S-EPMC3050327 | biostudies-literature

Organometallic enantiomeric scaffolding. Sequential semipinacol/1,5-"Michael-like" reactions as a strategic approach to bridgehead-quaternary center aza[3.3.1]bicyclics: application to the total synthesis of (-)-adaline.

Project description:A nontraditional approach to the enantiocontrolled construction of quaternary center-bearing heteroatom-bridged bicyclo[3.3.1]nonanes (homotropanes) is reported that is based on organometallic enantiomeric scaffolding. This strategy takes advantage of the unique reactivity profiles of TpMo(CO)(2)(5-oxo-eta(3)-pyranyl) and TpMo(CO)(2)(5-oxo-eta(3)-pyridinyl) scaffolds, and features a molybdenum-mediated semipinacol/1,5-"Michael-like" reaction sequence to establish the quaternary center and synthesize the bridged bicyclic structure. An asymmetric total synthesis of (-)-adaline highlights this methodology.

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rac-(1R,2S,6R,7R)-4-{[(1E)-(2-Chloro-phen-yl)methyl-idene]amino}-1-isopropyl-7-methyl-4-aza-tricyclo-[5.2.2.0]undec-8-ene-3,5-dione.

Project description:The title compound, C(21)H(23)ClN(2)O(2), was synthesized from N-amino-?-terpinene maleimide and 2-chloro-benzaldehyde. There are two independent mol-ecules in the asymmetric unit which are linked via an inter-molecular C-H?O hydrogen bond. The crystal studied was found to be a partial merohedral twin, with a 0.74?(7):0.26?(7) domain ratio.

| S-EPMC3089279 | biostudies-literature

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