Synthetic Applications of 2-(1,3-Dithian-2-yl)indoles. 7. Synthesis of Aspidospermidine

A new method of synthesizing the alkaloid aspidospermidine (1), based on building ring E on the pyridocarbazole [ABCD] ring structure, is reported. The preparation of the pyridocarbazole framework of Aspidosperma alkaloids is a new three-step synthetic application of 2-(1,3-dithian-2-yl)indoles. A tandem conjugate addition-alkylation reaction starting from indolyldithiane (4), 3-methylenelactam 6, and EtI yields the adduct 17. Treatment of lactam 17 with DIBALH leads to formation of the naphthyridoindole 18. Compound 18 isomerizes in aqueous AcOH to yield pyridocarbazole 3. Finally, closure of ring E and subsequent reduction of the dithiane ring produces aspidospermidine. Pyridocarbazoles 2 and 10 were prepared as models.     

Final elucidation of the absolute configuration of the signal metabolite hormaomycin

The complete absolute configuration of hormaomycin 1 a has been established by HPLC and HPLC/MS experiments with appropriately derivatized 4-propylprolines, (2S,4S)-6 and (2R,4R)-6, as well as 4-(Z)-propenylprolines, cis-5 and trans-5, and also feeding experiments with enantiomerically pure samples of the deuterium-labeled 3-(2'-nitrocyclopropyl)alanine, (2S)-3,3-[D2]15 and (2S)-2,2'-[D2]15, and 4-(Z)-propenylproline 2',4-[D2]-(2S,4R)-5. The latter five amino acids were prepared for the first time and allowed one to unequivocally assign the hitherto unknown absolute configurations of the last four stereocenters in hormaomycin 1 a. As a bonus, some new information about the biosynthesis of this molecule has also been gathered.     

Sterically congested tripodal phosphites: conformational analysis,solid-state polymorphism,metal complexation,and application to the asymmetric hydrosilation of ketones

The synthesis as well as isolation and crystallographic analysis of two solid-state polymorphs of the tripodal ligand tri[2,2',2' '-tris[(2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]ethyl]amine (3) is described. Form I crystallized from ethyl acetate in the space group P2(1)/n with the unit-cell parameters a = 20.070(10) A, b = 17.477(2) A, c = 27.620(3) A, and beta = 93.050(10) degrees, V = 9674.5(14) A(3), and Z = 4. Form II crystallized from a mixture of acetone and toluene in the space group P1 with the unit-cell parameters a = 12.493(1) A, b = 19.701(2) A, c = 21.027(2) A, alpha = 116.23(1) degrees, beta = 100.15(1) degrees, and gamma = 91.07(1) degrees, V = 4542 A(3), and Z = 2. Differences in the relative absolute stereochemistry of the stereoaxes in the seven-membered dibenzo[d,f][1,3,2]dioxaphosphepin ring are discussed. The synthesis and X-ray characterization of enantiomerically pure (S,S,S)-tri[2,2',2' '-tris[(2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]amine [(S,S,S)-7] are reported. Two crystallographically independent molecules exist in the unit cell that cannot be superimposed with each other by either a translation or a symmetry operation. The two solid-state conformers in the unit cell differed predominately by the absolute stereochemistry of the stereoaxes in the seven-membered dibenzo[d,f][1,3,2]dioxaphosphepin ring. The Rh(I)-catalyzed hydrosilation of acetophenone with the chiral ligands (R,R,S)-7 and (S,S,S)-7 showed significant differences in chiral induction. Chiral cooperativity between the stereoaxes and stereocenters in (S,S,S)-7 is observed. The mechanism of the communication between the stereocenters and stereoaxes leading to chiral cooperativity in the stereoselective transition state is suggested to be primarily steric in nature.     

Asymmetric synthesis of (+)-allo-quercitol and (+)-talo-quercitol via free radical cycloisomerization of an enantiomerically pure alkyne-tethered aldehyde derived from a carbohydrate.

We describe for the first time the free radical cyclization of enantiomerically pure alkyne-tethered aldehydes obtained from a carbohydrate (6, 7). The synthesis of compounds 6 and 7 obtained from a derivative of D-ribose is reported. These radical precursors have been submitted to cyclization with tributyltin hydride plus azobisisobutyronitrile to yield, after ring closure, two carbocycles, respectively. These carbocycles have been obtained as mixtures of E and Z vinyltin isomers, but with excellent diastereoselection at the new stereocenter formed during the ring closure. After protodestannylation, only one diastereomer was detected and isolated. The absolute configuration at the new stereocenter formed during the carbocyclization has been established by detailed (1)H NMR analysis. The specific transformation of 7-methoxymethoxy-2,2-dimethyl-4-methylene-5-tert-butyldimethylsilyloxy-(3aR,5S,7S,7aS)-perhydrobenzo[d][1,3]dioxole into optically pure (+)-allo-quercitol and (+)-talo-quercitol is described. From these results, we conclude that under an appropriate choice of radical precursors and conditions, the synthesis of highly functionalized cyclohexane derivatives of biological interest is now available.     

A new, non-iterative asymmetric synthesis of long-chain 1,3-polyols

A new approach to the asymmetric synthesis of pentadeca-1,3,5,7,9,11,13,15-octols and their derivatives is presented. It is based on the Sharpless asymmetric dihydroxylation (AD) of 4,4'-methylene[(1R,1'S,6R,6'S)-6-acetoxycyclohept-3-en-1-yl]bis(4-methoxybenzoate) (9), derived from a double [3+4] cycloaddition of the 1,1,3-trichloro-2-oxyallyl cation with 2,2'-methylenedifuran (1). The diol (-)-10, obtained in 98.4% ee from 9 with "AD-mix-beta(5x), was oxidised into (2R and 2S,4S,6R)-tetrahydro-2-hydroxy-6-((4S,6S)-(6-hydroxy-4-[(4-methoxybenzoyl)oxy]cyclohept-1-en-1-yl)-2-oxopropyl)-2H-pyran-4-yl 4-methoxybenzoates ((-)-18). By the combinations of Evans' anti and Nasaraka's syn reductions of aldol (-)-18 with the double Mitsunobu reaction, 16 diastereomeric pentadeca-1,3,5,7,9,11,13,15-octols and analogues can be obtained, in principle, with high enantio- and diastereoselectivities.     

Regioselective Intermolecular Cyclization of Methyl (E)-3-[(4S,5S)-5-Acetyl-2,2-dimethyl-1,3-dioxolan-4-yl)]prop-2-enoate

Russian Journal of Organic Chemistry - Methyl (E)-3-[(4S,5S)-5-acetyl-2,2-dimethyl-1,3-dioxolan-4-yl)]prop-2-enoate obtained from D-ribose eliminates water on storage and transforms into a bicyclic...     

Kinetic results implicating a polar radical reaction pathway in the rearrangement catalyzed by alpha-methyleneglutarate mutase

alpha-Methyleneglutarate mutase (MGM) catalyzes the rearrangement of 2-methyleneglutarate to 3-methylitaconate (2-methylene-3-methylsuccinate). A putative mechanism for the MGM-catalyzed reaction involves 3-exo cyclization of the 2-methyleneglutaric acid-4-yl radical to a cyclopropylcarbinyl radical intermediate that ring opens to the 3-hydroxycarbonyl-2-methylenebutanoic acid-4-yl radical (3-methylitaconic acid radical). Model reactions for this mechanism were studied by laser flash photolysis kinetic methods. alpha-Ester radicals were produced by 266 nm photolysis of alpha-phenylselenyl ester derivatives. Rate constants for cyclizations of the (Z)-1-ethoxycarbonyl-4-(2,2-diphenylcyclopropyl)-3-buten-1-yl radical ((Z)-8a) and (E)- and (Z)-1,3-di(ethoxycarbonyl)-4-(2,2-diphenylcyclopropyl)-3-buten-1-yl radicals ((E)- and (Z)-8b) were determined. The ester group in (Z)-8a accelerates the 3-exo cyclization in comparison to the parent radical lacking an ester group by a factor of 3, an effect ascribed to a polarized transition state. The ester groups at C3 in radicals 8b slow the 3-exo cyclization reaction by a factor of 50. The rate constant for cyclization of the 2-methyleneglutaric acid-4-yl radical is estimated to be k approximately 2000 s(-1) at ambient temperature. When coupled with the estimated partitioning of the intermediate cyclopropylcarbinyl radical, the overall rate constant for the conversion is estimated to be k approximately equal to 1 x 10(-3) s(-1), which is much too small for any radical reaction and several orders of magnitude too small for kinetic competence for the MGM-catalyzed process. The possibility that the radical reaction in nature involves an unusual mechanism in which polar effects are important is discussed.     

Synthesis of (2<Emphasis Type="Italic">S</Emphasis>,3<Emphasis Type="Italic">S</Emphasis>,4<Emphasis Type="Italic">S</Emphasis>)-2,3-<Emphasis Type="Italic">O</Emphasis>-isopropylidene-4-(methoxycarbonylmethyl)cyclopentan-1-one

(2S,3S,4S)-2,3-O-Isopropylidene-4-(methoxycarbonylmethyl)cyclopentan-1-one was synthesized starting from D-ribose through methyl (Z)-3-(5-acetyl-2,2-acetoxyacetyl-2,2-dimethyl-1,3-dioxolan-4-yl)prop-2-enoate which was subjected to cyclization in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, followed by decarboxylation.     

乌头碱A环中间体的合成

以(R)(-)香芹酮为原料,经环氧异构开环反应、［3+2］环加成应和Kemp消除反应等关键步骤,共9步反应合成了乌头碱A环中间体(1R,2R,4R,6S)-2-苯甲氧基-6-羟基-1-羟甲基-4-丙烯基环己烷腈,总收率25.7%;其结构经¹H NMR, ¹³C NMR, IR, MS(ESI)确证。     

5,6-二甲氧基-N-[(R)-4-甲氧基-2-(丙烯-2-基)-2,3-二氢苯并呋喃-5-基]-1,1a,2,7b-四氢环丙并[c]苯并吡喃-7b-基甲酰胺的合成与表征

鱼藤酮与氧硫叶立德反应得到关键中间体(5,6-二甲氧基-1,1a,2,7b-四氢环丙并[c]苯并吡喃-7b-基)[(R)-4-羟基-2-(丙烯-2-基)-2,3-二氢苯并呋喃-5-基]甲酮(2),2再通过醚化、肟化、贝克曼重排得到5,6-二甲氧基-N-[(R)-4-甲氧基-2-(丙烯-2-基)-2,3-二氢苯并呋喃-5-基]-1,1a,2,7b-四氢环丙并[c]苯并吡喃-7b-基甲酰胺(5),化合物的结构经1H NMR,MS和元素分析确认,采用单晶X射线衍射法确定化合物5的晶体结构.化合物5属于三斜晶系,P1空间群,晶胞参数:a=0.95772(5)nm,b=1.06591(6)nm,c=1.30112(7)nm,α=111.8460(10)°,β=109.8870(10)°,γ=93.0870°,V=1.13429(11)nm3,Z=2,Dc=1.281 g/cm3,μ(Mo Kα)=0.092 mm-1,F(000)=464.     

Model study for steroidal d/c ring closure in olefinic cyclization reactions; a mindo/3 study

MINDO/3 molecular orbital calculations are performed for the ring closure of (Z)- and (E)-allkenes as a model for the D/C ring closure to steroids. It is shown that a lower activation energy is needed for cyclizations in the chair configuration, than for cyclizations in the boat configuration. An analogous picture is found by comparison of (E)- and (Z)-alkenes. Cyclization of the (E)-alkene in the chair or boat configuration is energetically favoured over the ring closure of (Z)-alkenes. These results are in agreement with the Stork-Eschenmoser hypothesis.     

Synthesis and some transformations of 3-(2,2-dimethyloxan-4-yl)-4-methylpentanenitrile

2,2-Dimethyloxane-4-carbaldehyde reacted with ethyl cyanoacetate to give ethyl 2-cyano-3-(2,2-dimethyloxan-4-yl)prop-2-enoate whose reaction with isopropylmagnesium bromide afforded ethyl 2-cyano-3-(2,2-dimethyloxan-4-yl)-4-methylpentanoate. Elimination of the ester group from the latter led to the formation of 3-(2,2-dimethyloxan-4-yl)-4-methylpentanenitrile.     

Synthesis and Fungicidal Activity of Substituted (E)-3-Phenyl-1-(pyridin-3-yl)prop-2-en-1-one (E,Z)-O-Alkyl- and O-Benzyloximes

Russian Journal of Organic Chemistry - Previously unknown substituted (E)-3-phenyl-1-(pyridin-3-yl)prop-2-en-1-one (E,Z)-O-alkyl- and O-benzyloximes were synthesized by oximation of...     

Synthesis and coordination behavior of planar-chiral ferrocene alkenylphosphines

A series of planar-chiral ferrocene alkenylphosphines, (S(p))-2-(diphenylphosphino)-1-vinylferrocene (2), (S(p))-2-(diphenylphosphino)-1-(prop-1-en-1-yl)ferrocene (3; as a mixture of Z and E isomers in ca. 5:1 ratio), and (E,S(p))-2-(diphenylphosphino)-1-(2-phenylethen-1-yl)ferrocene ((E)-4), was obtained by Wittig and Horner-Wadsworth-Emmons reactions from the common precursor, (S(p))-2-(diphenylphosphino)ferrocene-1-carboxaldehyde (1). Coordination properties of these novel ferrocene donors were studied in their palladium(II) and tungsten(0)-carbonyl complexes. The reaction between 2 and [{Pd(mu-Cl)(L(NC))}2] (5, L(NC) = 2-{(dimethylamino)methyl-kappaN}phenyl-kappaC(1)) gave the bridge-cleavage product [PdCl(L(NC))(2-kappaP)] (6) while the reaction with [Pd(L(NC))(MeCN)2]ClO4 (7) yielded the cationic bis(chelate) [Pd(L(NC))(2-eta2:kappaP)]ClO4 (8). Chelate complexes of the type [W(CO)4(L-eta2:kappaP)] (9 with L = 2; (Z/E)-10 with L = (Z/E)-3) were obtained by reacting [W(CO)4(cod)] (cod = eta2:eta2-cycloocta-1,5-diene) with the appropriate phosphinoalkene in refluxing toluene while a similar reaction with (E)-4 yielded mixtures of [W(CO)5(4-kappaP)] ((E)-11) and [W(CO)4(4-eta2:kappaP)] ((E)-12). All compounds were characterized by spectral methods (multinuclear NMR, IR, MS, and CD), and the structures of 1, 2, 8, 9, (Z/E)-10, and (E)-11 were corroborated by X-ray diffraction analysis. Ligands 2 and (E)-4 as well as their complexes 6, 8, 9, (E)-11, and (E)-12 were further studied by electrochemical methods.     

Lipase-catalyzed resolution of (2R*,3S*)- and (2R*,3R*)-3-methyl-3-phenyl-2-aziridinemethanol at low temperatures and determination of the absolute configurations of the four stereoisomers

[reaction: see text] Lipase-catalyzed resolution of (2R*,3S*)-3-methyl-3-phenyl-2-aziridinemethanol, (+/-)-2, at low temperatures gave synthetically useful (2R,3S)-2 and its acetate (2S,3R)-2a with (2S)-selectivity (E = 55 at -40 degrees C), while a similar reaction of (2R*,3R*)-3-methyl-3-phenyl-2-aziridinemethanol, (+/-)-3, gave (2S,3S)-3 and its acetate (2R,3R)-3a with (2R)-selectivity (E = 73 at -20 degrees C). Compound (+/-)-2 was prepared conveniently via diastereoselective addition of MeMgBr to tert-butyl 3-phenyl-2H-azirine-2-carboxylate, (+/-)-1a, which was successfully prepared by the Neber reaction of oxime tosylate of tert-butyl benzoyl acetate 7a. The tert-butyl ester was requisite to promote this reaction. For determination of the absolute configuration of (2S,3R)-2a, enantiopure (2S,3R)-2 was independently prepared in three steps involving diastereoselective methylation of 3-phenyl-2H-azirine-2-methanol, (S)-10, with MeMgBr. The absolute configuration of (2S,3S)-3 was determined by X-ray analysis of the corresponding N-(S)-2-(6-methoxy-2-naphthyl)propanoyl derivative (S,S,S)-13.     

Effect of the β-substituent with respect to the azido group on the reactivity of methyl (2E)-3-[5-(azidomethyl)-2,2-diethyl-1,3-dioxolan-4-yl]-2-methylprop-2-enoate

Unlike methyl (2E)-3-[5-(azidomethyl)-2,2-diethyl-1,3-dioxolan-4-yl]-2—methylprop-2-enoate which is stable on storage, its acyclic derivative, methyl (2E,4S,5S)-6-azido-5-hydroxy-2-methyl-4-(pent-3-yloxy) hex-2-enoate at 20°C undergoes unusual decomposition with formation of exo-methylidenepyrrolidine. Analogous transformation was also observed in the epoxide ring opening in methyl (2E)-2-methyl-4-[(S)-oxiran-2-yl]-4-(pent-3-yloxy)but-2-enoate and in the substitution reaction of ethyl 5,6-bis(methanesulfonyloxy)-2-methyl-4-(pent-3-yloxy)hex-2-enoate with azide ion. Opening of the oxirane ring in the former by the action of azide ion was accompanied by formation of oxazetidine derivative as a minor product. The major intramolecular cyclization products, 4-hydroxy- and 4-mehtanesulfonyloxypyrrolidines were converted into stable pyrrole derivatives via elimination of the leaving groups. The hydrogenation of methyl and ethyl (2E)-3-[5-(azidomethyl)-2,2-diethyl-1,3-dioxolan-4-yl]-2-methylprop-2-enoates over palladium catalyst afforded the expected reduction products.     

金鸡钠碱催化烯胺的不对称C-亚磺酰化反应

以金鸡钠碱催化烯胺的不对称C-亚磺酰化反应,产物(E,Z)-N-苄氧羰基-2-苯亚磺酰基-1-苯基丙烯胺[(E,Z)-4],收率71%,立体选择性E:Z=3:2,其中(E)-4和(Z)-4的对映选择性分别为75%ee和93%ee。     

Syntheses and Crystal Structures of （S）-Methyl 2-（4-R-phenylsulfonamido）-3-（1H-indol-3-yl）propanoate （R = H （1） and Cl （2））

The title compounds （S）-methyl-2-（4-R-phenylsulfonamido）-3-（1H-indol-3- yl）propanoate （R = H （1）, Cl （2）） have been synthesized and their crystal structures also have been determined by X-ray single-crystal diffraction. Compound 1 （C18H18N2O4S） belongs to orthorhombic, space group P212121 with a = 9.6348（14）, b = 11.1517（17）, c = 16.412（3） A, V = 1763.4（5） A^3, Mr = 358.40, Z = 4, De = 1.350 g/cm^3,/t = 0.209 mm^-1, F（000） = 752, R = 0.0348 and wR = 0.0714. Compound 2 （CI8H17ClN2O4S） crystallizes in orthorhombic, space group P212121 with a = 9.3128（14）, b = 10.9655（16）, c = 17.783（3） A, V = 1815.9（5） A^3, Mr = 392.85, Z = 4, De = 1.437 g/cm^3, p = 0.352 mm^-1, F（000） = 816, R = 0.0389 and wR = 0.0845. The absolute structure Flack parameters X of compounds 1 and 2 are -0.03（8） and -0.06（7）, respectively. X-ray analysis reveals that the crystal structures of these two compounds both involve two intermolecular N-H…O hydrogen bond＇s.     

Synthesis and biological activities of optical isomers of 2-(4-diphenylmethyl-1-piperazinyl)ethyl 5-(4,6-dimethyl-2-oxo-1,3,2-dioxaphosphorinan-2-yl)-1,4-dihydro-2,6-dim ethyl-4-(3-nitrophenyl)-3-pyridinecarboxylate dihydrochloride (NIP-101).

Six optical isomers of 2-(4-diphenylmethyl-1-piperazinyl)ethyl 5-(4,6-dimethyl-2-oxo-1,3,2-dioxaphosphorinan-2-yl)-1,4-dihydro-2, 6-dimethyl-4-(3-nitrophenyl)-3-pyridinecarboxylate dihydrochloride (NIP-101, 1.2HCl.2H2O), a potent calcium antagonist, were successfully prepared by using optically active (2R,4R)-(-)- and (2S,4S)-(+)-2,4-pentanediols, and cis-2,4-pentanediol and optically active (S)-(+)-2-methoxy-2-phenylethanol. Their proton nuclear magnetic resonance investigations demonstrate that the 1,3,2-dioxaphosphorinane group is conformationally constrained around the C-P bond. Calcium-antagonistic and hypotensive activities of the optical isomers were examined and found to depend mainly on the absolute configuration at a stereogenic center in the 1,4-dihydropyridine ring rather than the configuration of the 1,3,2-dioxaphosphorinane moiety.     

Direct synthesis of NNN-donor enantiopure scorpionate ligands by an efficient diastereoselective nucleophilic addition to imines

New enantiopure imines (1-9) with a chiral substrate to control the stereochemistry of a newly created stereogenic center have been synthesized by reaction of the commercially available (1R)-(-)-myrtenal and different primary amines. The diastereomerically enriched lithium-scorpionate compounds [Li(κ(3)-mobpza)(THF)] (10) (mobpza = N-p-methylphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-mobpza)(THF)] (11) (mobpza = N-p-methoxyphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-fbpza)(THF)] (12) (fbpza = N-p-fluorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), and [Li(κ(3)-clbpza)(THF)] (13) (clbpza = N-p-chlorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide) were obtained by a diastereoselective 1,2-addition of an organolithium reagent to imines in good yield and with good diastereomeric excess (ca. 80%). The complexes [LiCl(κ(2)-R,R-fbpzaH)(THF)] (14) and [LiCl(κ(2)-R,R-clbpzaH)(THF)] (15) were obtained in enantiomerically pure form by the treatment of THF solutions of 12 or 13 with NH(4)Cl. The enantiomerically pure amines (R,R-mbpzaH) (16), (R,R-mobpzaH) (17), (R,R-fbpzaH) (18), and (R,R-clbpzaH) (19) were obtained by hydrolysis of the lithium-scorpionate compounds 10-13 with H(2)O. The lithium compound 12 was reacted with [TiCl(4)(THF)(2)] or [ZrCl(4)] to give the enantiopure complexes [MCl(3)(κ(3)-R,R-fbpza)] [M = Ti (20), Zr (21)]. The amine compound 18 reacted with [MX(4)] (M = Ti, X = O(i)Pr, OEt; M = Zr; X = NMe(2)) to give the complexes [MX(3)(κ(3)-R,R-fbpza)] (22-24). The reaction of Me(3)SiCl with [Zr(NMe(2))(3)(κ(3)-R,R-fbpza)] (24) in different molar ratios led to the halide-amide-containing complexes [ZrCl(NMe(2))(2)(κ(3)-R,R-fbpza)] (25) and [ZrCl(2)(NMe(2))(κ(3)-R,R-fbpza)] (26) and the halide complex 21. The isolation of only one of the three possible diastereoisomers of complexes 25 and 26 revealed that chiral induction from the ligand to the zirconium center took place. The structures of these compounds were elucidated by (1)H and (13)C{(1)H} NMR spectroscopy, and the X-ray crystal structures of 5, 12, 14, 15, and 24 were also established.