- Cobalt versus Osmium: Control of Both trans and cis Selectivity in Construction of the EFG Rings of Pectenotoxin 4
-
Catalytic oxidative cyclisation reactions have been employed for the synthesis of the E and F rings of the complex natural product target pectenotoxin 4. The choice of metal catalyst (cobalt- or osmium-based) allowed for the formation of THF rings with either trans or cis stereoselectivity. Fragment union using a modified Julia reaction then enabled the synthesis of an advanced synthetic intermediate containing the EF and G rings of the target.
- Roushanbakhti, Ahria,Liu, Yifan,Winship, Paul C. M.,Tucker, Michael J.,Akhtar, Wasim M.,Walter, Daryl S.,Wrigley, Gail,Donohoe, Timothy J.
-
supporting information
p. 14883 - 14887
(2017/10/24)
-
- Intramolecular thermal stepwise [2 + 2] cycloadditions: Investigation of a stereoselective synthesis of [n.2.0]-bicyclolactones
-
Fused cyclobutanes are found in a range of natural products and formation of these motifs in a straightforward and easy manner represents an interesting synthetic challenge. To this end we investigated an intramolecular variant of the thermal enamine [2 + 2] cyclisation, developing a diastereoselective intramolecular enamine [2 + 2] cyclisation furnishing δ lactone and lactam fused cyclobutenes in good yield and excellent diastereoselectivity.
- Throup, Adam,Patterson, Laurence H.,Sheldrake, Helen M.
-
supporting information
p. 9554 - 9559
(2016/10/22)
-
- Total synthesis of phorboxazole A via de novo oxazole formation: Strategy and component assembly
-
The phorboxazole natural products are among the most potent inhibitors of cancer cell division, but they are essentially unavailable from natural sources at present. Laboratory syntheses based upon tri-component fragment coupling strategies have been developed that provide phorboxazole A and analogues in a reliable manner and with unprecedented efficiency. This has been orchestrated to occur via the sequential or simultaneous formation of both of the natural product's oxazole moieties from two serine-derived amides, involving oxidation-cyclodehydrations. The optimized preparation of three pre-assembled components, representing carbons 3-17, 18-30, and 31-46, has been developed. This article details the design and syntheses of these three essential building blocks. The convergent coupling approach is designed to facilitate the incorporation of structural changes within each component to generate unnatural analogues, targeting those with enhanced therapeutic potential and efficacy.
- Wang, Bo,Hansen, T. Matthew,Wang, Ting,Wu, Dimao,Weyer, Lynn,Ying, Lu,Engler, Mary M.,Sanville, Melissa,Leitheiser, Christopher,Christmann, Mathias,Lu, Yingtao,Chen, Jiehao,Zunker, Nicholas,Cink, Russell D.,Ahmed, Feryan,Lee, Chi-Sing,Forsyth, Craig J.
-
p. 1484 - 1505
(2011/04/16)
-
- Stereoselective synthesis of tetrahydropyranyl diarylheptanoids (-)-centrolobine and (+)-centrolobine
-
A versatile chiron approach to the tetrahydropyranyl diarylheptanoid natural products (-)-centrolobine and (+)-centrolobine has been described. The use of an aldol reaction followed by reductive etherification for the formation of tetrahydropyran ring is of importance. Georg Thieme Verlag Stuttgart · New York.
- Reddy, Chada Raji,Madhavi, Pasupulety Phani,Chandrasekhar, Srivari
-
experimental part
p. 123 - 126
(2011/02/26)
-
- Benzimidazole compound
-
An object of the present invention is to provide a novel chemical compound useful as a therapeutic or prophylactic agent for acid-related diseases, having an excellent inhibitory effect against gastric acid secretion, an excellent effect of maintaining the inhibitory effect against gastric acid secretion, thereby maintaining intragastric pH high for a long time, and having more safety and appropriate physicochemical stability. Provided is a compound represented by where R1 and R3 may be the same or different and each represent a hydrogen atom or a C1-C6 alkyl group; R2 represents (5,5-dimethyl-1,3-dioxan-2-yl)methoxy group, 5,7-dioxaspiro[2.5]oct-6-ylmethoxy group, 1,5,9-trioxaspiro[5.5]undec-3-ylmethoxy group, or (2,2-dimethyl-1,3-dioxan-5-yl)methoxy group; R4, R5, R6 and R7 represent a hydrogen atom, halogen atom, C1-C6 alkyl group, C1-C6 haloalkyl group, C1-C6 alkoxy group or C1-C6 haloalkoxy group; and W1 represents a single bond, methylene or ethylene group, a salt thereof or a solvate of these.
- -
-
Page/Page column 86
(2008/06/13)
-
- On the stereochemistry of palmerolide A
-
Degradative studies of the anticancer macrolide palmerolide A have resulted in re-assignment of the C-7, C-10, and C-11 stereocenters.
- Lebar, Matthew D.,Baker, Bill J.
-
p. 8009 - 8010
(2008/03/18)
-
- Asymmetric 1,3-dipolar cycloaddition of nitrones with an electron-withdrawing group to allylic alcohols utilizing diisopropyl tartrate as a chiral auxiliary
-
The asymmetric 1,3-dipolar cycloaddition of nitrones possessing an electron-withdrawing group to allylic alcohols was achieved by the use of diisopropyl (R,R)-tartrate as a chiral auxiliary to afford the corresponding isoxazolidines with high regio-, diastereo-, and enantioselectivity. In the case of nitrones possessing an electron-withdrawing cyano or t-butoxycarbonyl group, 1,3-dipolar cycloaddition to 2-propen-1-ol occurred to produce the corresponding 3,5-trans-isoxazolidines with high enantioselectivity. To the contrary, nitrones possessing an amide moiety afforded the corresponding optically active 3,5-cis-isoxazolidines with completely opposite diastereoselectivity. A catalytic asymmetric 1,3-dipolar cycloaddition of nitrones possessing the N,N-diisopropylamide moiety to allylic alcohols was achieved to afford di- or trisubstituted isoxazolidines with excellent enantioselectivity of up to over 99% ee. The present asymmetric 1,3-dipolar cycloaddition was applied to the synthesis for the (2S,4R)-4-hydroxyornithine derivative.
- Ding, Xia,Taniguchi, Katsumi,Hamamoto, Yoshihira,Sada, Kazunori,Fujinami, Shuhei,Ukaji, Yutaka,Inomata, Katsuhiko
-
p. 1069 - 1083
(2007/10/03)
-
- Rational synthesis of contra-thermodynamic spiroacetals by reductive cyclizations
-
A synthesis of spiroacetals was developed using a reductive cyclization strategy that leads stereoselectively to spiroacetals with a single anomeric stabilization. The method begins with the synthesis of spiro ortho esters. The ortho ester is converted to a cyano acetal. Reductive lithiation of the cyano acetal generates an axial dialkoxylithium reagent, and intramolecular cyclization produces a new ring with retention of configuration. The strategy is convergent and produces complex spiro acetals in only a few steps. The method will be useful in the synthesis of natural products and will facilitate the synthesis of previously inaccessible contra-thermodynamic acetals. Copyright
- Takaoka, Leo R.,Buckmelter, Alexandre J.,LaCruz, Thomas E.,Rychnovsky, Scott D.
-
p. 528 - 529
(2007/10/03)
-
- Total synthesis of the potent antitumor polyketide (-)-callystatin A
-
A highly convergent and efficient total synthesis of the potent antitumor polyketide (-)-callystatin A is described. The synthesis required 19 steps from N-propionyl oxazolidinone 23 and produced the desired product in 3.5% overall yield.
- Dias, Luiz C.,Meira, Paulo R. R.
-
p. 4762 - 4773
(2007/10/03)
-
- Total synthesis of (+)-phorboxazole A, a potent cytostatic agent from the sponge Phorbas sp.
-
A convergent total synthesis of phorboxazole A (1a), from the C(3-19), C(20-27) and C(33-46) fragments 5, 4 and 91, respectively, concentrating on stereocontrolled formation of the bonds at C(2-3), C(19-20) and C(27-28), is described. Although a coupling reaction between a macrolide ketone and the side chain substituted sulfone, at C(27-28) was not successful, a Wadsworth-Emmons olefination involving the oxane methyl ketone 4 and an oxazole produced the oxane 90 which was next coupled to 91 leading to the C(20-46) unit 100. A further coupling of 100 to 71c at C(19-20) then led to 105, ultimately, and the synthesis was completed by a macrocyclisation reaction from 105, at the C(2-3) alkene bond, followed by deprotection of 106.
- Pattenden, Gerald,Gonzalez, Miguel A,Little, Paul B,Millan, David S,Plowright, Alleyn T,Tornos, James A,Ye, Tao
-
p. 4173 - 4208
(2007/10/03)
-
- Ester derivatives
-
This invention relates to compounds which exhibit selective muscarinic M3 receptor antagonism, have little side effects, are suitable for inhalation therapy and are useful as treating agents of respiratory system diseases, of the general formula (I); 1[in which A signifies a group expressed by a formula (a0) or (b0); 2Ar signifies optionally substituted aryl or heteroaryl; B1 and B2 signify aliphatic hydrocarbon; R1 signifies fluorine-substituted cycloalkyl; R2, R3 and R4 signify lower alkyl, single bond or alkylene bonded to B1, or R2 and R3 are united to signify alkylene; R5 and R7 signify hydrogen, lower alkyl, or a single bond or alkylene bonded to B2; R6 signifies hydrogen, lower alkyl or a group expressed as —N(R8)R9; and X?signifies an anion].
- -
-
Page/Page column 40-41
(2008/06/13)
-
- Enantioselective syntheses of monotetrahydrofuran annonaceous acetogenins tonkinecin and annonacin starting from carbohydrates
-
The total synthesis of two mono-THF acetogenins, tonkinecin (1) and annonacin (2), is reported in full detail. Terminal acetylene 3 prepared from D-glucono-δ-lactone and asymmetric dihydroxylation was employed as a common intermediate for both targets 1 and 2. Pd(0)-catalyzed coupling reaction of 3 with vinyl iodides 4 and 5, the chiral centers of which were taken from D-xylose and S-(-)-ethyl lactate, afforded enyne 26 and 27, respectively. Selective hydrogenation of 26 or 27 with diimide followed by removal of MOM ethers completed the synthesis of 1. A coupling reaction between the lithium derivative of 3 and epoxide 6 in the presence of boron trifluoride etherate gave 42. Both chiral centers in epoxide 6 were taken from L-ascorbic acid. Subsequent catalytic hydrogenation and MOM protection led to 43b. Introduction of the butenolide moiety by aldol condensation of protected S-lactal followed by cleavage of all MOM ethers completed the synthesis of 2.
- Hu,Yu,Wu,Wu
-
p. 853 - 861
(2007/10/03)
-
- The first total synthesis of annonacin, the most typical monotetrahydrofuran annonaceous acetogenins.
-
The first total synthesis of annonacin (1) was achieved by a highly convergent synthetic strategy. All the stereogenic centers were derived from three natural hydroxy acids respectively, except that those at C19 and C20 were produced from a Sharpless AD reaction.
- Hu,Wu,Wu
-
p. 887 - 889
(2007/10/03)
-
- Synthetic studies towards phorboxazole A. A convergent synthesis of the C31-C46 polyene oxane-hemiacetal side chain
-
A convergent and stereoselective synthesis of the C31-C46 side chain unit in the marine natural product phorboxazole A, which accommodates five asymmetric centres, three carbon-to-carbon double bonds and an oxane- hemiacetal unit, is described.
- Pattenden, Gerald,Plowright, Alleyn T.,Tornos, James A.,Ye, Tao
-
p. 6099 - 6102
(2007/10/03)
-
- Enantio- and diastereoselective synthesis of isoxazolidines by asymmetric 1,3-dipolar cycloaddition of nitrones
-
The asymmetric 1,3-dipolar cycloaddition of nitrones possessing electron withdrawing group to an achiral allyl alcohol was achieved by the use of diisopropyl (R,R)-tartrate as a chiral auxiliary to afford the corresponding isoxazolidines with high regio-, diastereo- and enantioselectivity.
- Ukaji, Yutaka,Taniguchi, Katsumi,Sada, Kazunori,Inomata, Katsuhiko
-
p. 547 - 548
(2007/10/03)
-
- Highly enantioselective and regioselective catalytic dihydroxylation of homoallylic alcohol derivatives
-
The catalytic dihydroxylation of p-methoxyphenyl ethers of various homoallylic alcohols proceeds with excellent enantioselectivity and in the case of diolefins with regioselectivity due to the favorable influence of the aryl ether moiety, as predicted from a previously proposed transition-state model.
- Corey,Guzman-Perez, Angel,Noe, Mark C.
-
p. 3481 - 3484
(2007/10/02)
-
- A Difference CD Method for Determining Absolute Stereochemistry of Acyclic 1,2,4-Triols
-
A general method based on difference circular dichroic (DIF CD) spectroscopy for assigning the absolute configuration of 1,2,4-triol is presented.Four possible stereoisomers of 6-heptene-1,2,4-triol were prepared and served as models to develop the procedure.The sign of the DIF CD Cotton effect is correlated to the absolute configuration of the C2 position.
- Mori, Yuji,Furukawa, Hiroshi
-
p. 6725 - 6738
(2007/10/02)
-
- Stereoselective Additions of Chiral, Functionalized Organozinc Reagents to Achiral and Chiral Aldehydes: a Matched-Mismatched Case in Organozinc Chemistry
-
The additions of the enantiomerically pure organozinc reagents 17 and 33 to the THF-aldehyde 1 in the presence of the monodentate Lewis acid boron trifluoride-ether give the nonchelation-controlled addition products 7 and 36, respectively (stereoselectivity 95:5, 86:14).These results provide a route to oligo(tetrahydrofuran)s with the relative stereochemistry trans-syn-cis.A stereodirecting effect of the chiral center in the organozinc reagent 17 is found, leading to simple diastereoselectivies in the reaction with achiral aldehydes and to a matched-mismatched case in the reaction with the chiral aldehyde 1. - Key Words: Addition, stereoselective, nonchelation-controlled / Reagent, organozinc / Stereodifferentiation, double / Oligo(tetrahydrofuran)
- Koert, Ulrich,Wagner, Holger,Pidun, Ulrich
-
p. 1447 - 1458
(2007/10/02)
-
- Towards a new type-of HMG-COA reductase inhibitor
-
In an attempt to design a novel class of HMG-Co A reductase inhibitors, we have synthesized compound as a reaction intermediate analogue of the enzymatic reduction of mevaldic acid by NADPH. A 15 steps, enantioselective sequence allowed us, from commercial R-(+)-malic acid to prepare aldehyde in an optically pure form and to couple it with the nicotinamide moiety affording the target molecule.
- Barth,Bellamy,Renaut,Samreth,Schuber
-
p. 6731 - 6740
(2007/10/02)
-
- THE ABSOLUTE CONFIGURATION EFFECT ON THE ACTIVITY OF THE AVOCADO ROOTING PROMOTER
-
16-Heptadecyn-1,2,4-triol is the most active component of the avocado rooting promotor (ARP).All four diastereoisomers of this compound have been synthesized.Their root promoting activity was determined over the physiologically active concentration range.It was found that the (2R,4R)-stereoisomer exerts a rooting activity similar to that of the extracted and purified compound from avocado tissues.The (2R,4S), and (2S,4R)-stereoisomers had lower activity and the (2S,4S)-stereoisomer had the lowest activity.It is concluded that the natural form, (2R,4R), acts in the rooting process either in its original structure or after reaction which does not alter its chiral centres.
- Becker, D.,Sahali, Y.,Raviv, M.
-
p. 2065 - 2067
(2007/10/02)
-
- The Synthesis of Optically Pure Epoxyalkyl β-D-Glucosides and β-Cellobiosides as Active-Site Directed Inhibitors of Some β-Glucan Hydrolases
-
(2R)- and (2S)-2,3-Epoxypropyl, (3R)- and (3S)-3,4-epoxybutyl and (4S)-4,5-epoxypentyl β-D-glucopyranoside, together with the (3R)- and (3S)-3,4-epoxybutyl β-cellobioside, have been prepared by condensation of a glycosyl bromide with the appropriate enantiomer of a chiral alcohol containing a diol protected as an isopropylidene acetal, and subsequent manipulation of the unmasked diol to the epoxide function.As well, in an improvement to the whole process, both diastereoisomers of the various epoxypropyl and epoxybutyl glycosides were available, from just the one enantiomer of the alcohol by an alternative manipulation of the diol.Finally, precursors to 2,3-epoxy-4-hydroxybutyl β-D-glucosides and β-cellobiosides were prepared in high optical purity by Sharpless asymmetric epoxidation of the appropriate 4-hydroxybutyl-2-enyl glycosides.
- Rodriguez, Evelyn B.,Scally, Gavin D.,Stick, Robert V.
-
p. 1391 - 1405
(2007/10/02)
-
- THE CHEMISTRYL OF L-ASCORBIC AND D-ISOASCORBIC ACIDS. 3: EFFICIENT SYNTHESES OF PURE R- AND S-1,2-O-ISOPROPYLIDENE-1,2,4-BUTANETRIOLS
-
Both enantiomers of 1,2-O-isopropylidene-1,2,4-butanetriol were prepared by two different and simple methods starting from readily available L-ascorbic and D-isoascorbic acids.
- Saibaba, Rasha,Sarma, Mallela S. P.,Abushanab, Elie
-
p. 3077 - 3086
(2007/10/02)
-
- Preparation of Derivatives of (R)-1,2,4-Butanetriol from L-Ascorbic Acid
-
Methyl 3,4-O-isopropylidene L-threonate (3), obtained from L-ascorbic acid, was converted to its O-phenyl thiocarbonate 4.Deoxygenation of 4 with tri-n-butyltin hydride gave the protected 3,4-dihydroxybutanoate 5, which was converted to the (R)-1,2,4-butanetriol derivatives 6 and 7.
- Luk, Kin-Chun,Wei, Chung-Chen
-
p. 226 - 228
(2007/10/02)
-
- STEREOCONTROLLED SYNTHESIS OF 6-epi-D-PURPUROSAMINE B BY IODOCYCLOCARBAMATION OF A CHIRAL Z-OLEFIN DERIVED FROM L-ALANINE AND L-MALIC ACID
-
6-epi-D-Purpurosamine B was synthesized efficiently through a chiral Z-olefin 8 derived from L-alanine and L-malic acid under complete stereochemical control by using iodocyclocarbamation as the key reaction.
- Kamiyama, Keiji,Urano, Yasuharu,Kobayashi, Susumu,Ohno, Masaji
-
p. 3123 - 3126
(2007/10/02)
-
- L-(S)-ERYTHRULOSE : THE SYNTHESYS OF (R)-1,2,4-BUTANETRIOL AND OF SOME RELATED C4 CHIRONS.
-
L-(S)-Erythrulose can easily be transformed into (R)-1,2,4-butanetriol and related C4 chiral building blocks.A formal synthesis of (-)-GABOB is presented.Also the formation of 3-methylene-1,2,4-butanetriol derivatives is described.
- Eycken, E. Van der,Wilde, H. De,Deprez, L.,Vandewalle, M.
-
p. 4759 - 4760
(2007/10/02)
-
- PREPARATION OF ETHYL 5(S),6-EPOXY-3(R)-(METHOXYMETHOXY)HEXANOATE: A KEY CHIRAL INTERMEDIATE FOR MEVINOLIN AND COMPACTIN.
-
The synthesis of Ethyl 5(S),6-Epoxy-3(R)-(methoxymethoxy)hexanoate, a key chiral synthon for the β-hydroxy-δ-lactone portion of Mevinolin and Compactin, via a regiospecific ring opening of a tetrahydrofuran derivative by dimethyboron bromide, is described.
- Guindon, Yvan,Yoakim, Christiane,Bernstein, Michael A.,Morton, Howard E.
-
p. 1185 - 1188
(2007/10/02)
-