- Enantiospecific Total Syntheses of (+)-Hapalindole H and (?)-12-epi-Hapalindole U
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Enantiospecific total syntheses of (+)-hapalindole H and (?)-12-epi-hapalindole U as well as the formal syntheses of (+)-hapalindole Q and (+)-12-epi-fischerindole U isothiocyanate have been described. Key steps of our approach feature expedient, highly regio- and diastereoselective Lewis acid catalyzed Friedel–Crafts reaction of indole with cyclic allylic alcohols and intramolecular reductive Heck reaction. Efficiency of the synthetic route also relies on an alkynyl aluminate complex driven regioselective nucleophilic epoxide opening from a sterically hindered site.
- Dethe, Dattatraya H.,Das, Saikat,Kumar, Vijay B.,Mir, Nisar A.
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supporting information
p. 8980 - 8984
(2018/06/04)
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- Enantiospecific total syntheses and assignment of absolute configuration of cannabinol-skeletal carbazole alkaloids murrayamines-O and -P
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First enantiospecific total syntheses of the cannabinol-skeletal carbazole alkaloids murrayamines-O and -P isolated from root barks of Murraya euchrestifoli, have been accomplished by highly diastereoselective, Lewis acid catalyzed coupling reactions of commercially available monoterpenes with carbazole derivative, which in addition to confirming the structure also established the absolute configuration of the natural products. Synthesis of both natural products and their enantiomers was achieved with high atom economy, in a protecting-group free manner and in six steps longest linear sequence from commercially available aniline derivative and verbenol.
- Dethe, Dattatraya H.,Das, Saikat,Dherange, Balu D.,Mahapatra, Samarpita
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supporting information
p. 8347 - 8350
(2015/06/02)
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- MnO2/TBHP: A Versatile and User-Friendly Combination of Reagents for the Oxidation of Allylic and Benzylic Methylene Functional Groups
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In the presence of activated MnO2, tert-butyl hydroperoxide (TBHP) in CH2Cl2 is able to oxidize the allylic and benzylic methylene groups of different classes of compounds. I describe a one-pot oxidation protocol based on two sequential steps. In the first step, carried out at low temperature, MnO2 catalyses the oxidation of the methylene group. This is followed by a second step where reaction temperature is increased, allowing MnO2 both to catalyse the decomposition of unreacted TBHP and to oxidize allylic alcohols that could possibly be formed. The proposed oxidation procedure is generally applicable, although its efficiency, regioselectivity, and chemoselectivity are strongly dependent on the structure of the substrate. A simple and user-friendly synthetic procedure for the oxidation of allylic and benzylic methylene groups to the corresponding conjugated carbonyl derivatives is described. The proposed oxidation protocol is based on the combined use of MnO2 and tert-butyl hydroperoxide, and is generally applicable.
- Serra, Stefano
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p. 6472 - 6478
(2015/10/19)
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- Protecting group free enantiospecific total syntheses of structurally diverse natural products of the tetrahydrocannabinoid family
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A simple, highly diastereoselective, Lewis acid catalyzed Friedel-Crafts coupling of a cyclic allylic alcohol with resorcinol derivatives has been developed. The method was applied for the enantiospecific total syntheses of structurally diverse natural products such as machaeriol-D, Δ8-THC, Δ9-THC, epi-perrottetinene and their analogues. Synthesis of both natural products and their enantiomers has been achieved with high atom economy, in a protecting group free manner and in less than 6 steps, the longest linear sequence, in a very good overall yield starting from R-(+) and S-(-)-limonene.
- Dethe, Dattatraya H.,Erande, Rohan D.,Mahapatra, Samarpita,Das, Saikat,Kumar B., Vijay
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supporting information
p. 2871 - 2873
(2015/03/03)
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- Daucus carota and baker's yeast mediated bio-reduction of prochiral ketones
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Stereoselective reduction of prochiral ketones to the corresponding alcohols using biocatalysts has attracted much attention, from the viewpoint of green chemistry. Asymmetric reduction of indanone, tetralone and hydroxyl trimonoterpene ketones to the corresponding enantiomerically pure (S)-alcohols, using Daucus carota plant homogenate and fermented baker's yeast cells, is described. The present study illustrates the broad substrate selectivity of the dehydrogenase enzymes present in the D. carota in the synthesis of a wide range of chiral secondary alcohols of biological importance.
- Yadav, Jhillu S.,Reddy, Garudammagari S.K.K.,Sabitha, Gowravaram,Krishna, Avvaru D.,Prasad, Attaluri R.,Hafeez-U-R-Rahaman,Vishwaswar Rao, Katta,Bhaskar Rao, Adari
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p. 717 - 723
(2008/02/02)
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- Lipase-catalyzed resolution of p-menthan-3-ols monoterpenes: Preparation of the enantiomer-enriched forms of menthol, isopulegol, trans- and cis-piperitol, and cis-isopiperitenol
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A study on the enzymic resolution of the most common p-menthan-3-ol monoterpene isomers is described. Enantioenriched alcohols 1, 5, 10, 11 and 12 are obtained by means of the lipase-mediated kinetic acetylation of the corresponding racemic materials. The stereochemical aspects of the enzymic process have been investigated. We found that the structural features of the starting p-menthan-3-ol as well as the kind of lipase used, impacted strongly on the enantioselectivity of the resolution. The potentialities of this approach for preparative purposes are discussed.
- Serra, Stefano,Brenna, Elisabetta,Fuganti, Claudio,Maggioni, Francesco
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p. 3313 - 3319
(2007/10/03)
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- Thermal degradation of terpenes: Camphene, Δ3-carene, limonene, and α-terpinene
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Emissions from wood dryers have been of some concern for a number of years, and recent policy changes by the Environmental Protection Agency have placed emphasis upon the gaseous emissions that lead to the formation of particulate matter as small as 2.5 μm diameter. In this qualitative study, camphene, Δ3-carene, limonene, and α-terpinene were thermally degraded in the presence of air to determine the number and kind of oxidative degradation products that might be expected under drying conditions used in processing wood products. Various chromatographic methods were used to isolate the products for proof of structure by NMR and/or GC-MS. The degradation products resulted from dehydrogenations, epoxidations, double bond cleavages, allylic oxidations, and rearrangements. A number of compounds not previously associated with the thermal degradation of these terpenes were identified. Emissions from wood dryers have been of some concern for a number of years, and recent policy changes by the Environmental Protection Agency have placed emphasis upon the gaseous emissions that lead to the formation of particulate matter as small as 2.5 μm diameter. In this qualitative study, camphene, Δ3-carene, limonene, and α-terpinene were thermally degraded in the presence of air to determine the number and kind of oxidative degradation products that might be expected under drying conditions used in processing wood products. Various chromatographic methods were used to isolate the products for proof of structure by NMR and/or GC-MS. The degradation products resulted from dehydrogenations, epoxidations, double bond cleavages, allylic oxidations, and rearrangements. A number of compounds not previously associated with the thermal degradation of these terpenes were identified.
- Mcgraw, Gerald W.,Hemingway, Richard W.,Ingram Jr., Leonard L.,Canady, Catherine S.,Mcgraw, William B.
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p. 4029 - 4033
(2007/10/03)
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- BIOTRANSFORMATION OF LIMONENE AND RELATED COMPOUNDS BY ASPERGILLUS CELLULOSAE
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The biotransformation of (+)-, (-)- and (+/-)-limones by Aspergillus cellulosae M-77 has been investigated. (+)-Limonene was transformed mainly to (+)-isopiperperitenone, (+)-limonene-1,2-trans-diol, (+)-cis-carveol and (+)-perilly alcohol, along with the minor formation of isopiperitenol and α-terpineol, whereas (-)-limonene was transformed to (-)-perillyl alcohol, (-)-limonene-1,2-trans-diol and (+)-neodihydrocarveol as the major products, along with the minor products such as (-)-isopiperitenone.In the case of the DL-form, perillyl alcohol, limonene-trans-1,2-diol, isopiperitenone and α-terpineol were also formed. 1-Methylcyclohexene and cyclohexene were also transformed to 3-methyl-2-cyclohexenone and 2-cyclohexenone via the corresponding alcohols, respectively.Key Word Index: Aspergillus cellulosae; biotransformation; (+)-, (-)- and (+/-)-limones; isoperitenone; limonene-1,2-trans-diol; cis-carveol; α-terpineol; 1-methylcyclohexene; cyclohexene; 3-methyl-2-cyclohexenone; 2-cyclohexenone.
- Noma, Yoshiaki,Yamasaki, Sumika,Asakawa, Yoshinori
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p. 2725 - 2728
(2007/10/02)
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- Total Synthesis of (+)-Balanitol and of (+)-Selin-4-(15)-ene-1β,11-diol
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(+)-Balanitol (1) and (+)-selin-4-(15)-ene-1β,11-diol (2), two recently isolated naturally occurring eudesmanoid bicyclic sesquiterpene alcohols, have been synthesized stereoselectively by a route involving a photocycloaddition of a cyclobutene and
- Anglea, Timothy A.,Pinder, A. Reginald
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p. 5537 - 5544
(2007/10/02)
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- The Structure of 3-Carene Nitrosate, (3R,3'R,4R,4'R)-(E)-Di(8-nitrooxy-6-menthen-3-yl)diazene N,N'-Dioxide. An Unusual Product of a Nitrosation Reaction
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The structure of the nitrosate, prepared from (+)-3-carene (1) (by nitrosation with isoamyl nitrite and nitric acid in acetic aciid at -20 deg C) was elucidated by chemical and spectroscopic methods.The structure of the product, known as "d-karene nitrosa
- Harmatha, Juraj,Samek, Zdenek,Stroemberg, Sture,Norin, Tornbjoern
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p. 459 - 466
(2007/10/02)
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