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Influence of the Production Process on the Key Aroma Compounds of Rum: From Molasses to the Spirit
The production of rum consists of fermentation, distillation, and aging. To check the influence of each step on the final rum aroma, molasses, mash, distillate, and the final rum were analyzed using the sensomics concept. The changes in key aroma compounds were determined by application of aroma extract dilution analysis (AEDA) in combination with gas chromatography-mass spectrometry for identification and by stable isotope dilution assays (SIDAs) for quantitation. Odor activity values (OAVs; ratio of concentration to respective odor threshold) were calculated for the compounds determined in the rum and, finally, the rum aroma was successfully simulated by recombination. (E)-β-Damascenone showed by far the highest OAV (3280) in rum. Although this compound was determined already in molasses, its concentration increased significantly during distillation, indicating a thermolabile precursor. Vanillin, 4-ethylphenol, 2-methoxyphenol, 4-ethyl-2-methoxyphenol, and 2-methoxy-4-propylphenol are well-known compounds mainly stemming from the wood barrels used for aging and showed an OAV ≥ 1. Another important group of aroma-active compounds in rum were ethyl esters, for which a significant increase was determined during fermentation but also to a lesser extent during aging. Altogether, the concentrations of 68% of the aroma-active compounds increased during the process, demonstrating its influence on the overall rum aroma.
Franitza, Laura,Granvogl, Michael,Schieberle, Peter
p. 9041 - 9053
(2016)
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Decadienoates: Sex pheromone components of nettle caterpillars Darna trima and D. bradleyi
This study was undertaken to identify sex pheromone components of nettle caterpillars Darna trima and Darna bradleyi (Lepidoptera: Limacodidae) whose larvae defoliate oil palm, Elaeis guineensis, in southeast Asia. Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses of pheromone gland extracts revealed two antennally active compounds produced by female D. trima and two by female D. bradleyi. Molecular structures of these candidate pheromone components were identified by electron-impact and chemical-ionization mass spectrometry; retention-index calculations on DB-5, DB-23, and DB-210 columns; microanalytical treatments, as well as syntheses of 'auxilliary' compounds that facilitated identification of the compounds. The compounds from D. trima were 2-methylbutyl (E)-7,9-decadienoate (A) and (E)-2-hexenyl (E)-7,9-decadienoate (B); from D. bradleyi we identified methyl (E)-7,9-decadienoate (C), and isobutyl (E)-7,9-decadienoate (D). In field experiments in Malaysia, (S)-2-methylbutyl (E)-7,9-decadienoate (SA) in combination with B proved to be essential and synergistic pheromone components for attraction of male D. trima. (R)-2-Methylbutyl (E)-7,9-decadienoate (RA) had no behavioral activity. Compound D singly attracted male D. bradleyi, but addition of C to D at a 1:10 ratio significantly enhanced attractiveness of the bait. Synthetic pheromone blends were more effective trap baits than unmated female moths and could be developed for monitoring populations of D. trima and D. bradleyi in Asian oil palm plantations.
Sasaerila, Yorianta,Gries, Regine,Gries, Gerhard,Khaskin, Grigori,King, Skip,Chor Boo, Teo
p. 1969 - 1981
(2000)
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Structure-Elucidating Total Synthesis of the (Polyenoyl)tetramic Acid Militarinone C §
The (polyenoyl)tetramic acid militarinone C (1) heads a family of seven members. Before our work, the configuration of C-5 was unknown whereas the configurations of C-8′ and C-10′ were either (R,R) or (S,S). We synthesized the four stereoisomers of constitution 1, which conform with these insights. This included cross-coupling both enantiomers of the western building block (8) with both enantiomers of the eastern building block (9). The specific rotations of the resulting 1 isomers suggested that natural 1 is configured like the coupling partners (S)-8 and (R,R)-9. This conclusion was corroborated by degrading natural 1 to alcohol 35 and by proving its configurational identity with synthetic (R,R)-35.
Brückner, Reinhard,Drescher, Christian,Hamburger, Matthias,Keller, Morris,Potterat, Olivier
supporting information

(2020/03/30)

Asymmetric total synthesis of four stereoisomers of the sex pheromone of the western corn rootworm
A convergent synthesis of four stereoisomers of the sex pheromone of the western corn rootworm (8-methyldecan-2-yl propionate, 1) from commercially available chiral starting materials is reported. The key step was Julia–Kocienski olefination between chiral BT-sulfone and chiral aldehyde. This synthetic route provided the four stereoisomers of 1 in 24–29% total yield via a six-step sequence. The simple scale-up strategy provides a new way to achieve the asymmetric synthesis of the sex pheromone.
Sun, Zhi-Feng,Zhang, Tao,Liu, Jinyang,Du, Zhen-Ting,Zheng, Huaiji
(2018/03/30)

Synthesis method and application of diabrotica virgifera virgifera le conte sex pheromone
The invention belongs to the technical field of pesticide chemistry, and discloses a synthesis method and application of diabrotica virgifera virgifera le conte sex pheromone. The synthesis method comprises the steps of enabling chiral sulfone compounds, i.e., (S)-2-methylbutyl thiazolsulfone and (R)-2-methylbutyl thiazolsulfone to be respectively subjected to a Julia-Kocienski coupling reaction with chiral aldehyde compounds, i.e., (S)-6-aldehyde hexan-2-ol propionate and (R)-6-aldehyde hexan-2-ol propionate, and carrying out hydrogenation reduction on the product of the coupling reaction soas to obtain the diabrotica virgifera virgifera le conte sex pheromone. In addition, the diabrotica virgifera virgifera le conte sex pheromone prepared by the method can be applied to the prevention and control of diabrotica virgifera virgifera le conte. The synthetic route of the diabrotica virgifera virgifera le conte sex pheromone is simplified, fewer by-products are produced in the reaction, and the reaction yield is greatly increased.
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Paragraph 0073; 0092; 0105-0107

(2018/07/15)

Polyunsaturated C-Glycosidic 4-Hydroxy-2-pyrone Derivatives: Total Synthesis Shows that Putative Orevactaene Is Likely Identical with Epipyrone A
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
supporting information
p. 7525 - 7530
(2017/06/13)

Strictly Alternating Sequences When Copolymerizing Racemic and Chiral Acetylene Monomers with an Organo-Rhodium Catalyst
A racemic mixture and two chiral monomers of 2-methyl-1-butyl propiolate, i.e., rac1, R1, and S1, were stereoregularly polymerized with a catalyst, [Rh(norbornadiene)Cl]2, in methanol at 40 °C to obtain the corresponding helical racemic and two chiral polymers, Prac1, PR1, and PS1, and a copolymer, Pco. The 1H and 13C NMR spectra of the racemic and chiral polymers differed, although the NMR spectra of their monomers were the same. The structures of the Pco copolymers with different chiral monomer ratios were analyzed using 1D and 2D NMR, optical rotation, circular dichroism (CD), UV-vis, and computational methods to elucidate the stereochemical effect of the chiral monomers together with the polymerization mechanism. The temperature dependence of 1H and 13C NMR spectra in line shape and intensity indicated that the helical main chain undergoes restricted rotation around the ester methylene bonds ?O-CH2- through a three-site jump exchange called an accordion-like helix oscillation (HELIOS). The energetically preferred structures of the helical-sense polymers PR1 or PS1 were simulated using the MMFF94 program. The dependence of the NMR spectral line shapes, optical rotations, and calculated structures on the monomer feed clearly indicated that the copolymers alternatively incorporate R1 and S1 to generate one-handed helical-sense chains. Based on these results, a polymerization mechanism is proposed, explaining a strictly alternating copolymerization that yields helical chains.
Yoshida, Yoshiaki,Mawatari, Yasuteru,Sasaki, Takahiro,Hiraoki, Toshifumi,Wagner, Manfred,Müllen, Klaus,Tabata, Masayoshi
p. 1291 - 1301
(2017/03/09)

Rational Design of Thermodynamic and Kinetic Binding Profiles by Optimizing Surface Water Networks Coating Protein-Bound Ligands
A previously studied congeneric series of thermolysin inhibitors addressing the solvent-accessible S2′ pocket with different hydrophobic substituents showed modulations of the surface water layers coating the protein-bound inhibitors. Increasing stabilization of water molecules resulted in an enthalpically more favorable binding signature, overall enhancing affinity. Based on this observation, we optimized the series by designing tailored P2′ substituents to improve and further stabilize the surface water network. MD simulations were applied to predict the putative water pattern around the bound ligands. Subsequently, the inhibitors were synthesized and characterized by high-resolution crystallography, microcalorimetry, and surface plasmon resonance. One of the designed inhibitors established the most pronounced water network of all inhibitors tested so far, composed of several fused water polygons, and showed 50-fold affinity enhancement with respect to the original methylated parent ligand. Notably, the inhibitor forming the most perfect water network also showed significantly prolonged residence time compared to the other tested inhibitors.
Krimmer, Stefan G.,Cramer, Jonathan,Betz, Michael,Fridh, Veronica,Karlsson, Robert,Heine, Andreas,Klebe, Gerhard
p. 10530 - 10548
(2016/12/16)

Domino Methylenation/Hydrogenation of Aldehydes and Ketones by Combining Matsubara's Reagent and Wilkinson's Catalyst
The methylenation/hydrogenation cascade reaction of aldehydes or ketones through a domino process involving two ensuing steps in a single pot is realized. The compatibility of Matsubara's reagent and Wilkinson's complex give a combination that allows, under dihydrogen, the transformation of a carbonyl function into a methyl group. This new method is suitable to introduce an ethyl motif from aromatic and aliphatic aldehydes with total chemoselectivity and total retention of α-stereochemical purity. The developed procedure is also extended to the introduction of methyl groups from ketones.
Maazaoui, Radhouan,Pin-Nó, María,Gervais, Kevin,Abderrahim, Raoudha,Ferreira, Franck,Perez-Luna, Alejandro,Chemla, Fabrice,Jackowski, Olivier
supporting information
p. 5732 - 5737
(2016/12/14)

PROCESSES FOR THE SYNTHESIS OF CHIRAL 1-ALKANOLS
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 0212; 0213

(2016/12/01)

Asymmetric hydrogenation of allylic alcohols using ir?N,P-Complexes
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.
p. 8342 - 8349
(2018/05/23)

PROCESSES FOR THE SYNTHESIS OF CHIRAL 1-ALKANOLS
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 00109

(2015/07/23)

Studies on tridecaptin B1, a lipopeptide with activity against multidrug resistant Gram-negative bacteria
Previously other groups had reported that Paenibacillus polymyxa NRRL B-30507 produces SRCAM 37, a type IIA bacteriocin with antimicrobial activity against Campylobacter jejuni. Genome sequencing and isolation of antimicrobial compounds from this P. polymyxa strain show that the antimicrobial activity is due to polymyxins and tridecaptin B1. The complete structural assignment, synthesis, and antimicrobial profile of tridecaptin B1 is reported, as well as the putative gene cluster responsible for its biosynthesis. This peptide displays strong activity against multidrug resistant Gram-negative bacteria, a finding that is timely to the current problem of antibiotic resistance.
Cochrane, Stephen A.,Lohans, Christopher T.,Van Belkum, Marco J.,Bels, Manon A.,Vederas, John C.
supporting information
p. 6073 - 6081
(2015/06/08)

Directed orthometalation and the asymmetric total synthesis of N -deoxymilitarinone A and torrubiellone B
A diverted total synthesis (DTS) approach to the total synthesis of pyridone alkaloids N-deoxymilitarinone A (8) and torrubiellone B (10) has been developed. The common intermediate 14 was first assembled by a dual directed orthometalation process using a methoxymethyl group as directed metalation group. Other crucial steps include the assembly of polyenes under aldol condensation for DTS using general and concise strategy and diastereoselective synthesis of the syn-dimethyl array by an Evans aldol reaction.
Ding, Feiqing,William, Ronny,Leow, Min Li,Chai, Hua,Fong, Jacqueline Zi Mei,Liu, Xue-Wei
supporting information
p. 26 - 29
(2014/01/23)

Collective synthesis of 4-hydroxy-2-pyridone alkaloids and their antiproliferation activities
A collective synthesis of 4-hydroxy-2-pyridone alkaloids - specifically, pretenellin B, prebassianin B, farinosone A, militarione D, pyridovericin, and torrubiellone C - has been achieved. Key steps include using a strategic convergent method to synthesize the densely substituted pyridone key intermediate by Suzuki-Miyaura cross-coupling reaction, a divergent synthesis approach of target molecules by aldol condensation of pyridone intermediate with homologous aldehydes, and an iterative synthesis of homologous aldehydes with all-trans-polyene backbones. Interestingly, among the six tumor cell lines investigated, torrubiellone C was found to induce potent and apoptotic inhibitory activities on Jurkat T cells with IC50 values of 7.05 μM. Hence, this approach could potentially contribute to the synthesis of bioactive small-molecule libraries as well as drug discovery.
Ding, Feiqing,Leow, Min Li,Ma, Jimei,William, Ronny,Liao, Hongze,Liu, Xue-Wei
supporting information
p. 2548 - 2554
(2014/10/15)

A comparison between oxazoline-imidazolinylidene, -imidazolylidine, -benzimidazolylidene hydrogenation catalysts
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
p. 9969 - 9974
(2013/10/22)

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
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
p. 1829 - 1835
(2013/09/02)

Asymmetric synthesis and absolute configuration of streptophenazine G
The asymmetric synthesis of the antibacterial natural product, streptophenazine G, has been achieved by employing asymmetric alkylation and asymmetric aldol reactions using chiral oxazolidinones as the key steps. The originally proposed structure for streptophenazine G has been revised, and its absolute configuration has been determined to be 1′S,2′R,6′S. The asymmetric total synthesis of 6′-epi-streptophenazine G is also described.
Yang, Zhicai,Jin, Xiaomin,Guaciaro, Michael,Molino, Bruce F.
experimental part
p. 3191 - 3196
(2012/05/19)

Enantioselective sorption of alcohols in a homochiral metal-organic framework
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
supporting information; experimental part
p. 513 - 515
(2012/01/19)

Hierarchical chiral expression from the nano- to mesoscale in synthetic supramolecular helical fibers of a nonamphiphilic C 3-symmetrical π-functional molecule
The controlled preparation of chiral structures is a contemporary challenge for supramolecular science because of the interesting properties that can arise from the resulting materials, and here we show that a synthetic nonamphiphilic C3 compound containing π-functional tetrathiafulvalene units can form this kind of object. We describe the synthesis, characterization, and self-assembly properties in solution and in the solid state of the enantiopure materials. Circular dichroism (CD) measurements show optical activity resulting from the presence of twisted stacks of preferential helicity and also reveal the critical importance of fiber nucleation in their formation. Molecular mechanics (MM) and molecular dynamics (MD) simulations combined with CD theoretical calculations demonstrate that the (S) enantiomer provides the (M) helix, which is more stable than the (P) helix for this enantiomer. This relationship is for the first time established in this family of C3 symmetric compounds. In addition, we show that introduction of the wrong enantiomer in a stack decreases the helical reversal barrier in a nonlinear manner, which very probably accounts for the absence of a majority rules effect. Mesoscopic chiral fibers, which show inverted helicity, i.e. (P) for the (S) enantiomer and (M) for the (R) one, have been obtained upon reprecipitation from dioxane and analyzed by optical and electronic microscopy. The fibers obtained with the racemic mixture present, as a remarkable feature, opposite homochiral domains within the same fiber, separated by points of helical reversal. Their formation can be explained through an oscillating crystallization mechanism. Although C3 symmetric disk-shaped molecules containing a central benzene core substituted in the 1,3,5 positions with 3,3′-diamido-2,2′-bipyridine based wedges have shown peculiar self-assembly properties for amphiphilic derivatives, the present result shows the benefits of reducing the nonfunctional part of the molecule, in our case with short chiral isopentyl chains. The research reported herein represents an important step toward the preparation of functional mesostructures with controlled helical architectures.
Danila, Ion,Riobe, Francois,Piron, Flavia,Puigmarti-Luis, Josep,Wallis, John D.,Linares, Mathieu,Agren, Hans,Beljonne, David,Amabilino, David B.,Avarvari, Narcis
supporting information; experimental part
p. 8344 - 8353
(2011/07/08)

Pheromone synthesis. Part 243: Synthesis and biological evaluation of (3R,13R,1′S)-1′-ethyl-2′-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Paulownia bagworm, Clania variegata, and its stereoisomers
All of the four stereoisomers of (1′S)-1′-ethyl-2′-methylpropyl 3,13-dimethylpentadecanoate, the major component of the female sex pheromone of Clania variegata, were synthesized by employing olefin cross metathesis as the key reaction and starting from (R)- or (S)-2-methyl-1-butanol, (R)- or (S)-citronellal, and (S)-2-methyl-3-pentanol. Their bioassay revealed the (3R,13R,1′S)-isomer as the bioactive one, whose more efficient synthesis was achieved in two different ways by employing Wittig reaction as the key step.
Mori, Kenji,Tashiro, Takuya,Zhao, Boguang,Suckling, David M.,El-Sayed, Ashraf M.
experimental part
p. 2642 - 2653
(2010/05/18)

Pheromone synthesis. Part 240: Cross-metathesis with Grubbs I (but not Grubbs II) catalyst for the synthesis of (R)-trogodermal (14-methyl-8-hexadecenal) to study the optical rotatory powers of compounds with a terminal sec-butyl group
(R)-Trogodermal (14-methyl-8-hexadecenal), the sex pheromone of Trogoderma species of pest insects against stored products, and its (S)-isomer were synthesized by using olefin cross-metathesis between (R)- or (S)-7-methyl-1-nonene and 8-nonenyl acetate as the key step. This step was successful with Grubbs I but not with Grubbs II catalyst. The latter caused randomization of the carbon skeleton to give a mixture of abnormal products with both longer or shorter carbon chains than the desired product. The specific rotations of 18 newly and 6 previously synthesized compounds with a terminal sec-butyl group were measured to conclude them to be [α]D +3.5 to +6.5 or -3.6 to -6.4.
Mori, Kenji
experimental part
p. 3900 - 3909
(2009/09/08)

Synthesis of all the four stereoisomers of (1′S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Paulownia bagworm, Clania variegata
All the four stereoisomers of (1′S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Clania variegata, were synthesized by starting from (R)- or (S)-2-methylbutan-1-ol, (R)- or (S)-citronellal, and (S)-2-methylpentan-3-ol. Olefin cross metathesis was employed as the key reaction.
Mori, Kenji,Tashiro, Takuya
scheme or table
p. 3266 - 3269
(2009/09/05)

Total synthesis of (+)-bourgeanic acid utilizing o-DPPB-directed allylic substitution
The lichen metabolite (+)-bourgeanic acid has been synthesized utilizing a new strategy for the construction of propionate motifs relying on the o-DPPB-directed copper-mediated allylic substitution. This synthesis features the o-DPPB-directed allylic substitution employing a chiral Grignard reagent, Sharpless asymmetric epoxidation, and reductive epoxide ring opening with a higher order dimethylcuprate to set the four stereogenic centers of the aliphatic depside.
Reiss, Tomislav,Breit, Bernhard
supporting information; experimental part
p. 3286 - 3289
(2009/12/05)

Synthetic studies on homophymine A: stereoselective synthesis of (2R,3R,4R,6R)-3-hydroxy-2,4,6-trimethyloctanoic acid
An efficient and highly stereocontrolled synthesis of (2R,3R,4R,6R)-3-hydroxy-2,4,6-trimethyloctanoic acid, the β-hydroxy acid unit that acylates the N-terminus of homophymine A, has been devised starting from iodoethane and (S,S)-pseudoephedrine propionamide in 9 steps and 36% average overall yield. Comparison of the 1H and 13C NMR and optical rotation data of the resulting β-hydroxy acid with the natural fragment unambiguously verifies the configurational assignment as (2R,3R,4R,6R).
Bellotta, Filomena,D'Auria, Maria Valeria,Sepe, Valentina,Zampella, Angela
experimental part
p. 3659 - 3663
(2009/09/05)

9-Borabicyclo[3.3.2]decanes and the asymmetric hydroboration of 1,1-disubstituted alkenes
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.
supporting information; experimental part
p. 9218 - 9219
(2009/02/02)

Self-assembly of a homochiral nanoscale metallacycle from a metallosalen complex for enantioselective separation
(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
p. 1245 - 1249
(2008/12/23)

Electrophysiological and behavioral activity of secondary metabolites in the confused flour beetle, tribolium confusum
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
p. 525 - 539
(2008/09/17)

Asymmetric hydrogenation routes to deoxypolyketide chirons
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
p. 7162 - 7170
(2008/03/12)

Chiral aggregates formed from methylated tetraenoic fatty acids: Formation of both antipodes of chiral aggregates from a single enantiomer and time-dependent stereomutation
(Chemical Equation Presented) Formation and behaviors of chiral aggregates of methylated tetraenoic fatty acids (TE-FAs) were reported. In the C-24 TE-FA series, the aggregate prepared by dispersing an ethanol stock solution of C-24 TE-FA 1b into sodium phosphate buffer gave a strong positive Cotton effect, whereas the aggregate prepared from a methanol stock solution gave a negative Cotton effect. In the C-20 TE-FA series, the aggregate prepared from an ethanol stock solution of C-20 TE-FA 2b exhibited time-dependent chirality inversion.
Ma, Jianguo,Cheon, Hwan-Sung,Kishi, Yoshito
p. 319 - 322
(2008/02/03)

Synthesis of (4R,8R)- and (4S,8R)-4,8-dimethyldecanal: the common aggregation pheromone of flour beetles
The synthesis of (4R,8R)- and (4S,8R)-4,8-dimethyldecanal 1 and 1a has been achieved connecting the chiral building block (R)-2-methyl-1-bromobutane 4 with (R)- and (S)-citronellol derivatives. The key intermediate 4 was obtained optically pure in five steps from methyl (S)-3-hydroxy-2-methylpropionate 2.
Santangelo, Ellen M.,Corrêa, Arlene G.,Zarbin, Paulo H.G.
p. 5135 - 5137
(2007/10/03)

An efficient and general method for the synthesis of α,ω- difunctional reduced polypropionates by Zr-catalyzed asymmetric carboalumination: Synthesis of the scyphostatin side chain
A decrease in the number of linear synthetic steps and an increase in efficiency have been realized in the synthesis of the side chain of scyphostatin. An efficient and selective synthesis of α,ω- difunctional reduced polypropionates from methyl 3-hydroxy-2-methylpropionate through the use of a Zr-catalyzed asymmetric carboalumination has been developed (see scheme, TBS = tert-butyldimethylsilyl).
Tan, Ze,Negishi, Ei-Ichi
p. 2911 - 2914
(2007/10/03)

An improved synthesis of the scyphostatin side-chain
A formal synthesis of the lipophilic side-chain of scyphostatin has been achieved using a convergent synthesis, in 16% yield over six steps. This synthesis involves enzymatic desymmetrisation of a meso-diol, resolution of 2-methylbutan-1-ol, stereoselective hydrozirconation of a volatile acetylene and a Negishi-style cross coupling.
McAllister, Graeme D.,Taylor, Richard J. K.
p. 2551 - 2554
(2007/10/03)

Synthesis and odor evaluation of stereoisomers of imine derivatives in roasted spotted shrimp
All possible stereoisomers of imine derivatives 1-4. which have the characteristic roast odor of seafood, were synthesized. As a result of odor evaluation of all isomers, we found that each isomer has a different and characteristic odor of roasted seafood.
Tachihara, Toru,Ishizaki, Susumu,Kurohayashi, Yoshiko,Tamura, Hiroshi,Ikemoto, Youichi,Onuma, Atsushi,Yoshikawa, Keisuke,Yanai, Tetsuya,Kitahara, Takeshi
p. 274 - 279
(2007/10/03)

Approach toward the total synthesis of orevactaene. 2. Convergent and stereoselective synthesis of the C18-C31 domain of orevactaene. Evidence for the relative configuration of the side chain.
The synthesis of the C18-C31 subunit of orevactaene (1) in an enantioselective and convergent manner is reported. Four chiral centers in the structure (i.e., carbons 23, 25, 32, and 33) have unknown configuration; thus, a modular approach has been devised to link the two stereocenter-containing ends of the structure together via a trisubstituted olefin template to ultimately produce all possible diastereomers of the target. Keys to the success of this approach include (i) an efficient synthesis of four diastereomeric hydrophobic tails (C22-C29) of the molecule with two stereogenic centers at C23 and C25; (ii) the synthesis of three stereodefined trisubstituted olefins 37, 38, and 43 using palladium(0)-catalyzed hydrometalation and metallometalation; and (iii) the convergent assembly of the aforementioned sections by a 'one-pot' lithium/halogen exchange, boron/lithium exchange, borate ester saponification, and Suzuki cross-coupling followed by oxidative deprotection. The sequence provided the desired aldehydes 49 and 50 as single isomers in good yields. Compiled spectroscopic data from the literature and present work provides evidence that the relative configuration of the methyl groups in the side chain of orevactaene may be 1,3-syn, which will be confirmed when the total synthesis has been completed. These results have paved the way for a parallel synthesis approach to prepare all 16 possible stereoisomers of orevactaene so that the relative and absolute stereochemistry of this compound can be determined.
Organ, Michael G,Bilokin, Yaroslav V,Bratovanov, Svetoslav
p. 5176 - 5183
(2007/10/03)

One post stereoselective synthesis of chiral αω-diynes from bromoallenes and organobis(heterocuprates)
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
p. 109 - 118
(2007/10/03)

The use of chiral dithianes for the synthesis of chiral α-oxo-β-alkyl and chiral α-oxo-β-aryl esters
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
p. 1073 - 1076
(2007/10/03)

Regio- and stereochemical study of sex pheromone of pine sawfly; Diprion nipponica
Regio- and stereoisomers of 1,2,ω-trimethyldecyl propionate (ω = 5-9) were prepared from stereochemically pure chiral building blocks as sex pheromone candidates of a pine sawfly; Diprion nipponica. Among the synthesized candidates, (1S,2R,8S)-1,2,8-trimethyldecyl propionate was found to be the sex pheromone of D. nipponica, based on compatibility of its GC-MS data with that of the extract of females, and its significantly high pheromone activity in a field bioassay. The field bioassay of the synthesized compounds also revealed that (1S,2R,SR)-1,2,8-trimethyldecyl propionate, (1S,2R,7S)-1,2,7-trimethyldecyl propionate, and (1S,2R,6S)-1,2,6-trimethyldecyl propionate could attract male sawflies to some extent as pheromone mimics.
Tai, Akira,Syouno, Emi,Tanaka, Kazuki,Fujita, Morifumi,Sugimura, Takashi,Higashiura, Yasutomo,Kakizaki, Masashi,Hara, Hideho,Naito, Tikahiko
p. 111 - 121
(2007/10/03)

Synthesis of the four possible stereoisomers of N-2′-methylbutyl-2-Methylbutylamide, the sex pheromone of the longhorn beetle Migdolus fryanus westwood
The four stereoisomers of N-2′-methylbutyl-2-methylbutylamide, the sex pheromone of the longhorn beetle Migdolus fryanus, an economically important pest of sugarcane in South America, were synthesized. The key intermediate 2-methylbutan-1-ol is commercially available only in its (S)-(-)-form. The (R)-(+)-enantiomer was obtained optically pure from methyl (S)-(+)-3-hydroxy-2-methylpropionate in five steps.
Santangelo,Zarbin,Cass,Ferreira,Correa
p. 3685 - 3698
(2007/10/03)

An approach to open-chain 1,5-stereocontrol using a silyl group
Nucleophilic attack by an ethylcuprate on the α,β-unsaturated ketone 3 takes place anti to the silyl group to give largely (96:4) a single product 4, fragmentation of which removes the silyl group, and reveals a pair of stereogenic centres having an open-chain 1,5 relationship 9.
Fleming,Ramarao
p. 2185 - 2186
(2007/10/03)

New chiral hosts derived from dimeric tartaric acid: Efficient optical resolution of aliphatic alcohols by inclusion complexation
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
p. 3171 - 3176
(2007/10/03)

Action of L-aminoacylase and L-amino acid oxidase on 2-amino-3- methylpent-4-enoic acid [Δ(4)-dehydroisoleucine and alloisoleucine] stereoisomers: An alternative route to a stereochemically pure compound and the application to the synthesis of (R)-2-methylbutan-1-ol
The action of L-aminoacylase and L-amino acid oxidase on the stereoisomers of 2-amino-3-methylpent-4-enoic acid was examined, to secure stereochemically pure compounds related to L-alloisoleucine. A scalemic mixture [(2S,3R)- (90.0%), (2S,3S)(3.2%), (2R,3S)- (5.9%), (2R,3R)- (0.9%)] of the N-trifluoroacetyl derivatives of the title compound, which was prepared by an asymmetric Claisen rearrangement, was submitted to Aspergillus L-aminoacylase-catalyzed hydrolysis. Only the (2S,3R)- and (2S,3S)isomers were hydrolyzed to give the corresponding amino acids. The subsequent treatment of these isomers with Crotalus adamanteus L-amino acid oxidase afforded the pure (2S,3R)-isomer, related to L-alloisoleucine, in more than 99% stereochemically pure form. Moreover, the product was converted to L- alloisoleucine and (R)-2-methylbutan-1-ol via a chemoenzymatic procedure.
Bakke, Mikio,Ohta, Hiromichi,Kazmaier, Uli,Sugai, Takeshi
p. 1671 - 1677
(2007/10/03)

Pheromone synthesis, CXCVII. Synthesis of the enantiomers of 2-sec- butyl-4,5-dihydrothiazole and (1R,5S,7R)-3,4-dehydro-exo-brevicomin, pheromone components of the male mouse, Mus musculus
Two components [2-sec-butyl-4,5-dihydrothiazole (1) and 3,4-dehydro-exo- brevicomin (2)] of a male-produced pheromone of the mouse Mus musculus have been synthesized in optically active forms. The enantiomers of 1 were obtained with an enantiomeric purity of ca. 92% ee and were found to be readily racemizable. Asymmetric dihydroxylation was employed as the key reaction (15→16) allowing the preparation of (1R,5S,7R)-2 with ca. 94% ee.
Tashiro, Takuya,Mori, Kenji
p. 2167 - 2173
(2007/10/03)

Chemoenzymatic synthesis of (R)-(+)-2-methylbutan-1-ol, a chiral synthon for the preparation of optically active pheromones
Optically active (R)-(+)-2-methylbutan-1-ol (which is not commercially available) was prepared by a chemoenzymatic synthesis, in which the key step involved a reduction catalyzed by baker's yeast. The synthon was used in the synthesis of (R)-10-methyldodecan-1-yl acetate, the chiral methyl-branched pheromone of Adoxophyes sp.
Geresh, Shimona,Valiyaveettil, Thomas J.,Lavie, Yair,Shani, Arnon
p. 89 - 96
(2007/10/03)

Side chain methyl analogues of Δ8-THC
The synthesis of both side chain epimers of 1'- (4), 2'- (5), 3'-methyl- (6) and 4'-methyl-Δ8-tetrahydrocannobinol (7) has been carried out. The synthetic approach entailed the acid catalyzed condensation of the appropriate substituted resorcinol with menthadienol to provide the Δ8-THC analogue. Both isomers of 1'- (4) and 2'-Δ8-THC (5) were more potent than Δ8-THC, both in vitro and in vivo. The 3'-methyl isomers (6) were approximately equal in potency to Δ8-THC, and 4'-methyl-Δ8-THC was less potent. There was relatively little difference in potency between the epimers of 4, 5, and 6.
Huffman, John W.,Lainton, Julia A.H.,Banner, W. Kenneth,Duncan Jr., Sammy G.,Jordan, Robert D.,Yu, Shu,Dai, Dong,Martin, Billy R.,Wiley, Jenny L.,Compton, David R.
p. 1557 - 1576
(2007/10/03)

Synthetic study of AAL-toxins: Efficient construction of two vicinal diol moieties by asymmetric dihydroxylation
Asymmetric dihydroxylation has been applied to syntheses of two vicinal anti-diol moieties in key intermediates of AAL-toxins. The strategy allowed efficient construction of left- and right segments of AAL-toxin main chain.
Oikawa, Hideaki,Kagawa, Takashi,Kobayashi, Tomonori,Ichihara, Akitami
p. 6169 - 6172
(2007/10/03)

Pheromone Synthesis, CLXXVI: Synthesis of the four stereoisomers of 3,13-dimethylheptadecane, the major sex pheromone component of the western false hemlock looper
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
p. 1965 - 1970
(2007/10/03)

Synthesis of the Aliphatic Depside (+)-Bourgeanic Acid
The lichen metabolite (+)-bourgeanic acid (1) was synthesized in 12 steps and 3.4percent overall yield from (R)-2-methyl-1-iodobutane (53) by a sequence which confirmed that this aliphatic depside is the self-esterification product of (2S,3S,4R,6R)-2,4,6-trimethyl-3-hydroxyoctanoic acid.Alkylation of the enolate of (S)-N-propionylprolinol (48) with 53 gave the amide 60 which was transformed to (2R,4R)-2,4-dimethylhexanal (4).The latter was reacted with the crotylboronate 68, prepared from (S,S)-(-)-diisopropyl tartrate, to afford (3R,4S,5R,7R)-3,5,7-trimethyl-1-nonen-4-ol (65) as the major diastereomer.Protection followed by ozonolysis and oxidation furnished (-)-hemibourgeanic acid (2).The β-lactone 73 derived from 2 was used to acylate 65, and the resulting ester 74 was subjected to oxidative ozonolysis to yield (+)-1.
White, James D.,Johnson, Alan T.
p. 3347 - 3358
(2007/10/02)

Absolute configuration of main chain of AAL-toxins
AAL-toxins TA1 1 and TA2 2, host-specific toxins produced by Alternaria alternata, were degraded to 2-methylbutanol, 3-methylnonan-1,9-diol and N-protected 4-aminobutan-1,3-diol, which were further converted to (R)-MTPA esters. These esters were correlated with synthetic samples by comparison of their 500 MHz 1H-NMR spectra. The remaining stereocenters were determined by the comparison of 1H-NMR spectra of 6a and 7 derived from 1 and 2 with those of synthetic model compounds. These data conclude that AAL-toxins possess 2S, 4S, 5R, 11S, 13S, 14R and 15R configurations.
Oikawa, Hideaki,Matsuda, Isamu,Kagawa, Takashi,Ichihara, Akitami,Kohmoto, Keisuke
p. 13347 - 13368
(2007/10/02)

Synthesis of stereospecific esters and resolution of racemic alcohols with immobilized lipases
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
p. 85 - 87
(2007/10/02)