- Electrophysiological and behavioral activity of secondary metabolites in the confused flour beetle, tribolium confusum
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Several previous studies have addressed pheromone communication in various flour beetles (Coleoptera: Tenebrionidae), including the confused flour beetle, Tribolium confusum (du Val). Different stereoisomers of 4,8-dimethyldecanal (DMD) were reported as the only components of an aggregation pheromone, but the behavioral activity of DMD is low. In the present study, additional previously reported secondary metabolites (benzoquinones and hydrocarbons) were tested for electrophysiological activity (EAG) with both sexes of T. confusum. Two benzoquinones and three monoenic hydrocarbons elicited significant EAG activity from both male and female antennae. There was an elevated male EAG response (vs. the females) to two out of the three hydrocarbons and for both quinones. The EAG-active compounds were subsequently investigated for behavioral activity in a walking bioassay. Benzoquinones are considered toxic and have been assigned a function as alarm substances in flour beetles, but we found that methyl-1, 4-benzoquinone in intermediate concentrations was attractive to both male and female beetles and could therefore act as an aggregation pheromone component. Males were also attracted to ethyl-1,4-benzoquinone. The corresponding hydroquinones, presumed precursors of the benzoquinones, did not elicit any electrophysiological response and were not tested for behavioral activity. The unsaturated hydrocarbons (1-tetradecene, 1-pentadecene, and 1-hexadecene) elicited significant EAG responses from both male and female antennae and were also attractive in the behavioral assay. Our results show that several beetle-produced compounds, in addition to 4,8-dimethyldecanal, may be part of a complex pheromone system in flour beetles and play a role in mediating aggregation in T. confusum.
- Verheggen,Ryne,Olsson,Arnaud,Lognay,Hoegberg,Persson,Haubruge,Loefstedt
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Read Online
- Polyunsaturated C-Glycosidic 4-Hydroxy-2-pyrone Derivatives: Total Synthesis Shows that Putative Orevactaene Is Likely Identical with Epipyrone A
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Orevactaene and epipyrone A were previously thought to comprise the same polyunsaturated tail but notably different C-glycosylated 4-hydroxy-2-pyrone head groups. Total synthesis now shows that the signature bicyclic framework assigned to orevactaene is a chimera; the compound is almost certainly identical with epipyrone A, whose previously unknown stereochemistry has also been established during this study. Key to success was the ready formation of the bicyclic core of putative orevactaene by a sequence of two alkyne cycloisomerization reactions using tungsten and gold catalysis. Equally important was the flexibility in the assembly process gained by the use of heterobimetallic polyunsaturated modules whose termini could be selectively and consecutively addressed in a practical one-pot cross-coupling sequence.
- Preindl, Johannes,Schulthoff, Saskia,Wirtz, Conny,Lingnau, Julia,Fürstner, Alois
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supporting information
p. 7525 - 7530
(2017/06/13)
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- PROCESSES FOR THE SYNTHESIS OF CHIRAL 1-ALKANOLS
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The invention relates to highly enantioselective processes for the synthesis of chiral 1-alkanols via Zr-catalyzed asymmetric carboalumination of alkenes.
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Paragraph 0214; 0215; 0216; 0217
(2016/12/01)
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- Asymmetric hydrogenation of allylic alcohols using ir?N,P-Complexes
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In this study, a series of γ,γ-disubstituted and β,γ-disubstituted allylic alcohols were prepared and successfully hydrogenated using suitable N,P-based Ir complexes. High yields and excellent enantioselectivities were obtained for most of the substrates studied. This investigation also revealed the effect of the acidity of the N,P?Ir-complexes on the acid-sensitive allylic alcohols. DFT ΔpKa calculations were used to explain the effect of the N,P-ligand on the acidity of the corresponding Ir-complex. The selectivity model of the reaction was used to accurately predict the absolute configuration of the hydrogenated alcohols.
- Li, Jia-Qi,Liu, Jianguo,Krajangsri, Suppachai,Chumnanvej, Napasawan,Singh, Thishana,Andersson, Pher G.
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p. 8342 - 8349
(2018/05/23)
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- PROCESSES FOR THE SYNTHESIS OF CHIRAL 1-ALKANOLS
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The invention relates to highly enantioselective processes for the synthesis of chiral 1-alkanols via Zr-catalyzed asymmetric carboalumination of alkenes.
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Paragraph 00110; 00111
(2015/07/23)
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- A comparison between oxazoline-imidazolinylidene, -imidazolylidine, -benzimidazolylidene hydrogenation catalysts
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Imidazolinylidene, imidazolylidine, benzimidazolylidene complexes 1a-c were prepared and tested in asymmetric hydrogenations of a series of largely unfunctionalized alkenes. Similarities and differences in the catalytic performance of these complexes were rationalized in terms of the predicted mechanisms of these reactions, and their relative tendencies to generate protons under the hydrogenation conditions.
- Khumsubdee, Sakunchai,Fan, Yubo,Burgess, Kevin
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p. 9969 - 9974
(2013/10/22)
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- Widely applicable synthesis of enantiomerically pure tertiary alkyl-containing 1-alkanols by zirconium-catalyzed asymmetric carboalumination of alkenes and palladium- or copper-catalyzed cross-coupling
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A highly enantioselective and widely applicable method for the synthesis of various chiral 2-alkyl-1-alkanols, especially those of feeble chirality, has been developed. It consists of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and palladium- or copper-catalyzed cross-coupling. By virtue of the high selectivity factor (E) associated with iodine, either (S)- or (R)-enantiomer of 3-iodo-2-alkyl-1- alkanols (1), prepared by ZACA reaction of allyl alcohol, can be readily purified to the level of ≥99 % ee by lipase-catalyzed acetylation. A variety of chiral tertiary alkyl-containing alcohols, including those that have been otherwise difficult to prepare, can now be synthesized in high enantiomeric purity by Pd- or Cu-catalyzed cross-coupling of (S)-1 or (R)-2 for introduction of various primary, secondary, and tertiary carbon groups with retention of all carbon skeletal features. These chiral tertiary alkyl-containing alcohols can be further converted into the corresponding acids with full retention of the stereochemistry. The synthetic utility of this method has been demonstrated in the highly enantioselective (≥99 % ee) and efficient syntheses of (R)-2-methyl-1-butanol and (R)- and (S)-arundic acids. Look, mom, one hand! 2-Alkyl-1-alkanols of feeble chirality have been synthesized by a sequence of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and Pd- or Cu-catalyzed cross-coupling in high enantiomeric purity of ≥99 % ee. The synthetic utility of this method has been demonstrated in highly enantioselective and efficient syntheses of (R)-2-methyl-1-butanol, (R)- and (S)-arundic acids. Copyright
- Xu, Shiqing,Lee, Ching-Tien,Wang, Guangwei,Negishi, Ei-Ichi
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p. 1829 - 1835
(2013/09/02)
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- Synthesis of enantiomerically pure model compounds of the glucose-6-phosphate-T1-translocase inhibitors kodaistatins A-D. Inferences with regard to the stereostructure of the natural products
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The kodaistatins A and C (5a,b) inhibit a step in glucose-metabolism at ～100 nM concentrations. This makes them potential 'leads' in the therapy of diabetes. We elucidated the (S)-configuration of the side-chain stereocenter of kodaistatin A by ozonolysis/reduction. The 13C NMR shifts of kodaistatin A model cis-11 suggest that the diol moiety in the dihydroxycyclopentanone core of kodaistatin is trans-configured. This model was prepared from the Feringa lactone (21) and (S)-2-methylbutanal (27) in 23 steps (14 steps in the longest linear sequence). We employed the same strategy for the simplified kodaistatin A model iso-cis-12, which resulted from the same substrates in 11 steps (6 steps in the longest linear sequence). The cyclopentenone cores of both targets stemmed from a C4+C1 approach. The C4 components were masked 'tartaric ketones' (16a,b) and a masked 'tartaric aldehyde' (18), respectively. The C1 components were the lithium-derivatives of the side-chain bearing phosphonates 19 and 22, respectively. The desired acylation/deprotonation/Horner-Wadsworth- Emmons tandem reaction succeeded in a single operation with the 'tartaric aldehyde' 18 but required partly or exclusively additional operations when we incorporated the 'tartaric ketones' 16a or 16b, respectively. The 'tartaric ketones' 16a,b contained an α-siloxyethyl substituent. It is noteworthy that it had to be introduced by adding the benzyltrimethylammonium enolate of lactone 18 to acetaldehyde because the lithium enolate of this lactone fragmented by an acetone-releasing β-elimination.
- Wüster, Thomas,Kaczybura, Natasza,Brückner, Reinhard,Keller, Manfred
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p. 7785 - 7809
(2013/08/23)
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- Enantioselective sorption of alcohols in a homochiral metal-organic framework
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Single-crystal X-ray diffraction study reveals the host-guest interactions between a homochiral metal-organic framework and two enantiomers of a chiral alcohol providing the key driving force for the enantioselective sorption of alcohols in the framework.
- Suh, Kyungwon,Yutkin, Maxim P.,Dybtsev, Danil N.,Fedin, Vladimir P.,Kim, Kimoon
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supporting information; experimental part
p. 513 - 515
(2012/01/19)
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- Highly enantioselective iridium-catalyzed hydrogenation of α,β-unsaturated esters
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α,β-Unsaturated esters have been employed as substrates in iridium-catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic- and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. Asymmetric hydrogenation: A variety of α,β-unsaturated esters were hydrogenated with high enantioselectivities (see scheme). The hydrogenated products have been used in synthetic transformations as well as in formal total syntheses. Copyright
- Li, Jia-Qi,Quan, Xu,Andersson, Pher G.
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supporting information
p. 10609 - 10616
(2012/11/07)
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- Self-assembly of a homochiral nanoscale metallacycle from a metallosalen complex for enantioselective separation
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(Chemical Presented) Only half may enter: A homochiral porous nanoscale metallacycle has been efficiently self-assembled from semiflexible enantiopure metallosalen complexes with complementary coordination motifs. Single crystals of the macromolecule (see structure; C gray, Zn purple, O red, N blue) show a reversible and controllable dynamic behavior. Particularly, the metallacycle can be used to resolve small racemic alcohols with high enantioselectivity (over 99.0% ee).
- Li, Gao,Yu, Weibin,Ni, Jia,Liu, Taifeng,Liu, Yan,Sheng, Enhong,Cui, Yong
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p. 1245 - 1249
(2008/12/23)
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- 9-Borabicyclo[3.3.2]decanes and the asymmetric hydroboration of 1,1-disubstituted alkenes
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The syntheses of the optically pure asymmetric hydroborating agents 1 (a, R = Ph; b, R = TMS) in both enantiomeric forms are reported. These reagents are effective for the hydroboration of cis-, trans- and trisubstituted alkenes. More significantly, they exhibit unprecedented levels of selectivity in the asymmetric hydroboration of 1,1-disubstituted alkenes (28-92% ee), a previously unanswered challenge in the nearly 50 year history of this reagent-controlled process. For example, the hydroboration of α-methylstyrene with 1a produces the corresponding alcohol 6f in 78% ee (cf., Ipc2BH, 5% ee). Suzuki coupling of the intermediate adducts 5 produces the nonracemic products 7 very effectively (50-84%) without loss of optical purity. Copyright
- Gonzalez, Ana Z.,Roman, Jose G.,Gonzalez, Eduvigis,Martinez, Judith,Medina, Jesus R.,Matos, Karl,Soderquist, John A.
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supporting information; experimental part
p. 9218 - 9219
(2009/02/02)
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- Asymmetric hydrogenation routes to deoxypolyketide chirons
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Asymmetric hydrogenations of monoenes and dienes were performed to obtain terminal deoxypolyketide fragments A and the corresponding internal Chirons B and C. The chiral N-heterocyclic carbene catalyst 1 was used throughout. Modest selectivities for hydrogenations of simple monoenes relayed into high selectivities for preparations of the terminal deoxypolyketide fragments in which either two hydrogenations or one and an optically pure starting material were used. Curiously, the face selectivities for hydrogenation of α,β-unsaturated esters were consistently opposite to those that had been observed for styrene and stilbene derivatives in previous work, and to closely related allylic alcohol and ether derivatives in this work. Plausible mechanisms for this differing behavior were deduced by using DFT calculations. It appears that the origin of the unusual stereoselectivity for the ester derivatives is transient metal-coordination of the ester carbonyl whereas there is no evidence that the allylic alcohol or ethers coordinate. The routes developed to α,ω-functionalized internal deoxypolyketide fragments are extremely practical. These begin with the Roche ester being converted into alkene and, in one case, diene derivatives. Catalyst control prevails in the hydrogenations of these substrates, but there is a significant "substrate vector" (a term we used to describe the influence of the substrate on a catalyst-controlled reaction). This is determined by minimization of 1,3-allylic strain and, in some cases, syn pentane interactions. This substrate vector can be constructively paired with the (dominant) catalyst vector by use of the appropriate enantiomer of 1. In the hydrogenation of a diene derivative, two chiral centers could be formed simultaneously with overall 11:1.0 selectivity; this is the first time this has been achieved in any asymmetric synthesis of a deoxypolyketide fragment. Throughout, diastereo-selectivities of the crude material in the syntheses of α,ω-functionalized internal deoxypolyketide fragments were in excess of 11:1.0 and chromatographically purified samples could be isolated in high yields with dr (dr = diastereomeric ratio) values consistently in excess of 40:1.0.
- Zhou, Jianguang,Ogle, James W.,Fan, Yubo,Banphavichit, Yorawit,Zhu, Ye,Burgess, Kevin
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p. 7162 - 7170
(2008/03/12)
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- Nematocidal thiocyanatins from a southern Australian marine sponge Oceanapia sp.
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Investigations of a southern Australian marine sponge, Oceanapia sp., have yielded two new β methyl branched bisthiocyanates, thiocyanatins D 1 (3a) and D2 (3b), along with two new thiocarbamate thiocyanates, thiocyanatins E1 (4a) and E2 (4b). The new thiocyanatins belong to a rare class of bioactive marine metabolite previously only represented by thiocyanatins A-C (1, 2a/b). Structures were assigned on the basis of detailed spectroscopic analysis, with comparisons to the known bisthiocyanate thiocyanatin A (1) and synthetic model compounds (5-7). The thiocyanatins exhibit potent nematocidal activity, and preliminary structure-activity relationship investigations have confirmed key characteristics of the thiocyanatin pharmacophore.
- Capon, Robert J.,Skene, Colin,Liu, Edward Hsiang-Te,Lacey, Ernest,Gill, Jennifer H.,Heiland, Kirstin,Friedel, Thomas
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p. 1277 - 1282
(2007/10/03)
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- One post stereoselective synthesis of chiral αω-diynes from bromoallenes and organobis(heterocuprates)
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Organobis(heterocuprates), 7 and 8, have been prepared reacting in situ 1,4-dilithiobutane and di-Grignard reagents, obtained from 1,4-dibromobutane and 1,4-dibromobenzene, respectively, with CuSPh and LiCuBr2. The cross-coupling reaction of these di-cuprate reagents with 3-alkyl and 3,3-dialkyl 1-bromo-1,2-dienes (1) provides a general method for selective synthesis of 1,9-decadiynes (5) and 1,4-bis(2-propynyl)benzenes (6), characterized by two identical chiral centres in the α position to the triple bonds. The high 1,3-anti stereoselectivity of the coupling process allows us to obtain enantiomerically enriched α,ω-diynes 5 and 6 starting from optically active allenic substrates 1.
- Caporusso, Anna Maria,Aronica, Laura Antonella,Geri, Roberto,Gori, Marco
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p. 109 - 118
(2007/10/03)
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- The use of chiral dithianes for the synthesis of chiral α-oxo-β-alkyl and chiral α-oxo-β-aryl esters
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A number of chiral dithianes were synthesised using chiral auxiliary technology. These were then used as acyl anion equivalents in the synthesis of chiral α-oxo-β-alkyl and chiral α-oxo-β-aryl esters.
- Tyrrell, Elizabeth,Skinner, George A.,Janes, John,Milsom, Greig
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p. 1073 - 1076
(2007/10/03)
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- New chiral hosts derived from dimeric tartaric acid: Efficient optical resolution of aliphatic alcohols by inclusion complexation
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The novel, chiral, host compounds 8 and 9 were derived from tartaric acid. Inclusion complexation with these host compounds permitted highly efficient resolution of some aliphatic alcohols (10-13). The symmetrical dimer host compound 8 is effective for optical resolution of alcohols 10, 12, and 13 by a combination of enantioselective inclusion complexation and distillation techniques. The unsymmetrical dimer host compound 9 is effective for optical resolution of cyanohydrin 11. The crystal structures of the inclusion complexes were analyzed by X-ray diffraction methods in order to elucidate the mechanism of the efficient chiral recognition in the inclusion crystals.
- Tanaka, Koichi,Honke, Shinji,Urbanczyk-Lipkowska, Zofia,Toda, Fumio
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p. 3171 - 3176
(2007/10/03)
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- Sterically constrained tricyclic 2-oxazolidinone as excellent chiral auxiliary
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A new class of conformationally rigid 2-oxazolidinones with effectively bulky substituents, derived from the [4+2] cycloadduct of cyclopentadiene and a-oxazolone, serve as extremely powerful chiral auxiliaries for asymmetric alkylations, Diels-Alder reactions and conjugate addition reactions.
- Nakamura, Taiju,Hashimoto, Noriaki,Ishizuka, Tadao,Kunieda, Takehisa
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p. 559 - 562
(2007/10/03)
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- Pheromone Synthesis, CLXXVI: Synthesis of the four stereoisomers of 3,13-dimethylheptadecane, the major sex pheromone component of the western false hemlock looper
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All of the four stereoisomers of 3,13-dimethylheptadecane (1), the female-produced sex pheromone of the western false hemlock looper (Nepytia freemani), were synthesized by starting from the enantiomers of citronellol (2a) and 2-methyl-1-butanol (4a). VCH Verlagsgesellschaft mbH, 1996.
- Takikawa, Hirosato,Shirai, Yasuo,Kobayashi, Makoto,Mori, Kenji
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p. 1965 - 1970
(2007/10/03)
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- Total asymmetric syntheses of (1S,2S)-norcoronamic acid, and of (1R,2R)- and (1S,2S)-coronamic acids from the diastereoselective cyclization of 2-(N-benzylideneamino)-4-chlorobutyronitriles
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(3R)-2-(N-Benzylideneamino)-4-chloro-3-methylbutyronitrile 3, prepared from the commercially available methyl (2S)-3-hydroxy-2-methyl propionate 5 (96percent ee), readily underwent potassium carbonate induced cyclization to provide, after acid hydrolysis (6 N HCl) and chromatography, the (1S,2S)-norcoronamic acid 1a with 88percent diastereoselectivity and above 95percent enantiomeric excess.From (2R)-2-(hydroxymethyl)butyl acetate 23 (above 88percent ee) obtained by enzymatic enantioselective hydrolysis with lipase PS, was prepared the (3S)-2-(N-benzylideneamino)-3-(chloromethyl)valeronitrile 29, which after base-induced cyclization (K2CO3) and acid (6 N HCl) or basic (0.8 N NaOH) hydrolysis led to the non-natural (1R,2R)-coronamic acid 18 (>88percent ee).Also from this same acetate (2R)-23 was prepared the (3R)-3-(chloromethyl)-2-pentanenitrile 37, which provided the (1S,2S)-coronamic acid 17 (above 88percent ee) after base-induced cyclization (K2CO3 or LDA) and acid hydrolysis (6 N HCl).It is noteworthy that these short synthetic sequences, which do not require any expensive chiral auxiliary or optically active precursors, do not alter the enantiomeric purity of the stereogenic centers of these 2,3-methanoamino acids.However, the E diastereoselctivity of these cyclizations was not improved by using bulky N-(diphenylmethylene)amino substituent, contrary to results of some molecular mechanic calculations (MAD).
- Gaucher, Anne,Ollivier, Jean,Marguerite, Jacqueline,Paugam, Renee,Salauen, Jacques
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p. 1312 - 1327
(2007/10/02)
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- Synthesis of stereospecific esters and resolution of racemic alcohols with immobilized lipases
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Immobilization of lipases from two different sources has been carried out by covalent bonding with agarose activated by CNBr.The product has been trapped in a polymeric gel matrix, absorbed on celite or macroporous Amberlite IRA-938 resin.It has been confirmed that immobilized lipases prepared by using Amberlite IRA-938 are the most suitable biocatalysts for transesterification reactions.In these reactions, a matrix ester, racemic and nonracemic alcohols have been used as reactants.By using the immobilized lipases, the stereospecific esters have been synthesized.These esters give enantiomeric alcohols on hydrolysis in alkaline media.Thus, the resolution of racemic alcohols has been achieved.Boiling points and refractive indices of all the products have been determined.Specific rotations of optically active products have also been recorded.Analysis of products has been done using chromatographic and spectrophotometric techniques (TLC, GLC and IR).
- Sagiroglu, Ayten,Telefoncu, Azmi
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- Pheromone Synthesis, CXXV. Synthesis of the Four Possible Stereoisomers of 3,7-Dimethylnonadecane, the Female Sex Pheromone of Agromyza frontella Rondani
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The synthesis of the four possible stereoisomers of 3,7-dimethylnonadecane (1) has been achieved by starting from the enantiomers of methyl 3-hydroxy-2-methylpropanoate (2) and (R)-(+)-citronellic acid (3).
- Mori, Kenji,Wu, Jiang
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p. 213 - 217
(2007/10/02)
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- Synthetic Microbial Chemistry, XXIV. - Synthesis of Antibiotic 1233A, an Inhibitor of Cholesterol Biosynthesis
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A synthesis of 1233A -3,5,7-trimethyl-2,4-undecadienoic acid (1a)> was achieved by employing (R)-2-hydroxymethyl-3-butenyl acetate (2a) and (R)-citronellic acid (3) as chiral building blocks.The former was prepared by lipase-mediated asymmetric hydrolysis of the corresponding diacetate. Key Words: Antibiotic 1233A / Cholesterol biosynthesis, inhibitor of / β-Lactone / Lipase, asymmetric hydrolysis with / Sulfone, alkylation of
- Mori, Kenji,Takahashi, Yoshio
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p. 1057 - 1065
(2007/10/02)
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- TOTAL SYNTHESIS OF (-)-BETAENONE C
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Stereoselctive synthesis of (-)-betaenone C through intramolecular Diels-Alder reaction has made possible to provide pertinent intermediates for the biosynthetic study of betaenones.
- Ichihara, Akitami,Miki, Shokyo,Kawagishi, Hirokazu,Sakamura, Sadao
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p. 4551 - 4554
(2007/10/02)
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- Asymmetric Syntheses of Chiral Propane-1,3-diols Starting from Malonic Acid
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Syntheses of chiral intermediates having one tertiary asymmetric centre were carried out via chiral half-esters of monoalkylmalonic acids.The menthyl half-ester of ethylmalonic acid afforded a single diastereoisomer through crystallisation-induced asymmetric transformation (second-order asymmertic transformation).Furthermore enantioselective preparation of unsymmertical propane-1,3-diol derivatives was achieved by the use of 8-phenylmenthyl half-esters.
- Ihara, Masataka,Takahashi, Masanobu,Taniguchi, Nobuaki,Yasui, Ken,Fukumoto, Keiichiro,Kametani, Tetsuji
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p. 897 - 903
(2007/10/02)
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- Pheromones, 67. - Synthesis of the Enantiomers of (Z)-14-Methyl-8-hexadecenal , the Pheromone of Some Trogoderma Species (Coleoptera: Dermestidae)
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The separation of diastereomeric phenylglycinolamides of 2-methylbutyric acid by means of MPLC yields the pure enantiomers of the acid, from which (R,Z)- and (S,Z)-14-methyl-8-hexadecenal (1) (trogodermal) can be obtained.
- Bestmann, Hans Juergen,Frighetto, Rosa T. S.,Frighetto, Nelson,Vostrowsky, Otto
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p. 877 - 880
(2007/10/02)
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- Biohydrogenation of Unsaturated Compounds by Saccharomyces cerevisiae. Part 1. Stereochemical Aspects of the Reaction and Preparation of Useful Bifunctional Chiral Synthons
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Ethyl 4,4-dimethoxy-3-methylbut-2-enoate (1; R=CO2Et) has been prepared as a mixture of (E)- and (Z)-isomers, the (E)/(Z) ratio depending on the base used.Each isomeric mixture of (1a) and (1b) has been used as substrate for biohydrogenation with fermenting Saccharomyces cerevisiae (baker's yeast) and the (Z)-isomer seems to be the preferred substrate. (E)-Unsaturated alcohols such as (3a) and (5d) are not reduced to the corresponding saturated hydroxy derivatives by baker's yeast.The (E)-aldehyde (3c) and its acetal (3d) are mainly reduced to the corresponding (E)-alcohol (3a), the saturated hydroxy ester (2a) being formed to a minor extent, especially with (3d).In contrast, biohydrogenation is also successful with the (E)-isomers of compounds (3e), (3f), and (3b) (R2=alkyl or alkenyl).If the allylic oxygenated group to be reduced is not α-methyl substituted, reduction to the corresponding saturated alcohols readily occurs with the (E)-isomers as in the case of (5f).For this last biohydrogenation, the stereochemistry of the methyl-bearing carbon has been established by chemical correlations.The α,β-disubstituted allylic acetal (6a) is not biohydrogenated by the yeast, but a mixture of unsaturated hydroxy ester (6b) and γ-hydroxy lactone (8) is recovered from the incubation.
- Ferraboschi, Patrizia,Grisenti, Paride,Casati, Rosangela,Fiecchi, Alberto,Santaniello, Enzo
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p. 1743 - 1748
(2007/10/02)
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- Chiral Acetylenes as Synthetic Intermediates. 4. Synthesis and Chiroptical Properties of Optically Active α,β-Acetylenic Ketones
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The preparation of some optically active α,β-acetylenic ketones from chiral 1-alkynes or acid chlorides is reported along with the evaluatiun of the stereospecificity of the synthetic methods adopted.For the compounds prepared, the CD spectra are presented and discussed; Cotton effects are observed in correspondence with the n -> ?* and ? -> ?* transitions.In agreement with previous hypotheses, another electronic transition at ca. 250 nm is also measured in the CD spectra of the title compounds.
- Giacomelli, Giampaolo,Rosini, Carlo,Caporusso, Anna Maria,Palla, Fabio
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p. 4887 - 4891
(2007/10/02)
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