A synthesis of α-aminosulphonic acids

The α-aminosulphonic acid analogues of cysteine and methionine were prepared by sulphonation of the appropriate amines at their α-C atom using Sulfan. It is essential that moisture is excluded at all stages.     

Comparison of the isomeric α-amino acyl adenylates and amino acid phosphoramidates of adenosine by electrospray ionization tandem mass spectrometry

The isomeric α-amino acyl adenylates and amino acid phosphoramidates of adenosine were synthesized and analyzed in detail by electrospray ionization tandem mass spectrometry (ESI-MS(n)). In ESI-MS/MS of α-amino acyl adenylates, the novel rearrangement ion [cAMP-H](-) observed as the most intense signal was formed through the pentacoordinate phosphorus intermediate with a six-membered ring by nucleophilic attack of the 3'-hydroxyl group on the phosphorus atom. In contrast, for the amino acid phosphoramidate of adenosine, the phosphorus atom could be attacked not only by the carboxylic group to form the cyclic aminoacyl phosphoramidates (CAPAs), but also by the nitrogen atom on the nucleobase leading to intramolecular phosphoryl group migration. It was found that the sodium ion having multidentate binding ability played an essential role in this characteristic rearrangement. The proposed mechanisms were supported by the MS/MS study, deuterium-labeled experiments, high-resolution tandem mass spectrometry and moderate calculations at the B3LYP/6-31G* level. The characteristic fragmentation patterns of α-amino acyl phosphates and amino acid phosphoramidates allows identification of stereoisomers when either the phosphorylation is at the N-terminus or C-terminus of amino acids.     

Novel Rearrangements and Heterocyclisation of P-Imides

Abstract

The preliminary introduction of electron accepting dichlorophosphine group at nitrogen atom of N-monosub-stituted α-aminoketones or α-aminocarbon acid esters increases the mobility of the α-carbon hydrogen atom so, that the intermolecular O-phosphorylation is enabled.¹     

Selective reaction of amino acid sulfoximines with nitrous acid; facile stereospecific conversion to amino acid sulfoxides

N-Unsubstituted sulfoximines of amino acids can he readily converted to the corresponding amino acid sulfoxides in high yields by treatment with stoichiometric quantities of nitrous acid. Under the conditions employed, reaction with L-methionine-S (or R)-sulfoximine is specific for the sulfoximine nitrogen atom, and no reaction occurs at the α-amino group. Conversion to the sulfoxide proceeds with complete retention of configuration at the sulfur atom.     

α-乙酰基二硫缩烯酮α碳原子的酰化反应

进行了α-乙酰基二硫缩烯酮与酰氯的酰化反应. 以干燥的二氯甲烷为溶剂, 在四氯化钛催化下, α-乙酰基环二硫缩烯酮(1)可与脂肪及芳酰氯(2)反应, 在化合物1的α-碳原子上发生酰化反应, 以较高的产率生成各种α-乙酰基-α-酰基二硫缩烯酮(3).     

REVIEW CHARACTERISTIC REACTIONS OF THE ALKOXY GROUPS OF THE ACID DIESTERS OF PHOSPHOROUS ACID

Abstract

This review presents the characteristic reactions of the alkoxy group of the acid diesters of phosphorous acid (RO)₂ P(O)H: transesterification—with the phosphorus atom as the reaction center; alkylation—with the α-carbon atom as the reaction center; dealkylation—with the α-carbon atom as the reaction center. The possibilities of these reactions in the synthesis of end products with various structures and compositions are demonstrated. The perspectives for the practical application of these esters of phosphorous acid are discussed.     

Diastereoselective addition of α-substituted α-amino-H-phosphinates to imines using Yb(OTf)3 as an efficient Lewis acid catalyst

Diastereoselective addition of α-substituted α-amino-H-phosphinates to imines is described. Among Lewis acids, Yb(OTf)₃ was found to be the best catalyst. α,α′-Diaminophosphinic derivatives were obtained with de's ranging from 10 to 95% in the presence of Yb(OTf)₃ as an efficient Lewis acid catalyst. The reaction proceeded with retention of configuration at the phosphorus atom.     

Ring cleavage reactions of methyl α-D-allopyranoside derivatives with phenylboron dichloride and triethylsilane

In the course of our studies on the regioselective carbon-oxygen bond cleavage of the benzylidene acetal group of hexopyranosides with a reducing agent, we found that a combination of a Lewis acid and a reducing agent triggered a ring-opening reaction of the pyranose ring of methyl α-D-allopyranosides. The formation of an acyclic boronate ester by the attachment of a hydride ion at C-1 indicated that the unexpected endocyclic cleavage of the bond between the anomeric carbon atom and the pyranose ring oxygen atom proceeded via an oxacarbenium ion intermediate produced by the chelation between O5/O6 of the pyranoside and the Lewis acid, followed by nucleophile substitution with a hydride ion at C1.     

Syntheses of fluorinated ligands to probe binding of antigenic determinants of Vibrio cholerae O:1, serotypes Inaba and Ogawa,to antibodies

Derivatives of methyl α-glycosides of antigenic determinants of Vibrio cholerae O:1, serotypes Inaba and Ogawa, specifically fluorinated at position 2′ or 4′ have been synthesized by coupling the appropriately fluorinated derivatives of 3-deoxy-l-glycero-tetronic acid with the methyl α-glycosides of perosamine. The compound having the fluorine atom at position 2 was obtained by electrophilic addition of fluorine to the glycal derived from the parent antigenic determinant, serotypes Inaba, using Selectfluor^™ as a fluorination reagent.     

Synthesis of 2-aryl(hetaryl)-1-hydroxyimidazoles by the reaction of aliphatic 1,2-hydroxylamino oximes with aromatic and heteroaromatic aldehydes

A reaction of aliphatic 1,2-hydroxylamino oximes bearing the hydroxylamino group at the secondary carbon atom with aromatic and heteroaromatic aldehydes in acetic acid leads to the corresponding 1-hydroxy-2-aryl(hetaryl)-4,5-dialkylimidazoles in high yields. α-Aryl(hetaryl)-nitrones initially formed by the condensation of 1,2-hydroxylamino oximes with aldehydes are quantitatively converted to the corresponding imidazoles.     

Hydrogen abstraction by chlorine atom from amino acids: remarkable influence of polar effects on regioselectivity

Quantum chemistry computations have been used to investigate hydrogen-atom abstraction by chlorine atom from protonated and N-acetylated amino acids. The results are consistent with the decreased reactivity at the backbone α-carbon and adjacent side-chain positions that is observed experimentally. The individual effects of NH(3)(+), COOH, and NHAc substituents have been examined and reveal important insights. The NH(3)(+) group in isolation is found to be deactivating at the α-position, while the acetamido group is activating. For the COOH group, polar effects lead to a contrathermodynamic deactivation of the thermodynamically most favorable α-abstraction. In the N-acetylamino acid, the α-position is deactivated by the combined inductive effect of the substituents and the presence of an early transition structure, again overriding the greater thermodynamic stability of the α-centered radical product. Deactivation of the α-, β-, and γ-positions results in a peculiar stability for amino acids and peptides and their derivatives with respect to radical degradation.     

钼磷酸和2-吡啶-偶氮-2萘酚电荷转移配合物的合成、表征及性质研究

杂多化合物具有很强的接受电子能力,是一类优秀的受体分子,它可以与有机分子以氢键或配位键作用形成电荷转移配合物。由于这类配合物具有特殊的光、电、磁性质在催化、功能材料及药物化学等领域受到研究者的广泛关注[1]。有大量文献报道了杂多酸作为电子受体与有机给体相结合形成电子给一受型配合物,并在性能方面进行了探讨[2-3]。为了考察有机配体的位阻效应对配合物形成的影响,我们选择体积大,含有偶氨基及共轭π键的2-吡啶- 偶氮-2-萘酚（简写为PAN）为电子给体,12-钼磷酸（简写为PMo12）为电子受体,制备了新型标题化合物,并对…     

SYNTHESIS OF α-AMINOORTHOESTERS FROM O-TOSYLHYDROXIMATES

ABSTRACT

The abstraction of the acid hydrogen of O-tosylhydroximates 1 by sodium ethylate, then nucleophilic attack of the excess of sodium ethylate at the more hindred carbond atom of azirine 2 and aziridine 3 intermediates to give the α-aminoorthoesters (35–45% yields). The α-aminoorthoester 4a is transformed into α-iminoorthoesters 5a (63% yield) and α-amidoorthoester 6a (65% yield).     

反式-3-苯基-12-取代环十二酮的合成及晶体结构

以环十二酮为原料,经2-碘酰基苯甲酸(IBX)氧化制备2-环十二烯酮,在醋酸钯和三苯基磷催化下,2-环十二烯酮与苯硼酸反应制得3-苯基环十二酮.经3-苯基环十二酮与不同试剂发生区域选择性反应制备了一系列新的3-苯基-12-取代环十二酮衍生物,采用核磁共振波谱(NMR)和液相色谱-高分辨质谱(HRMS)表征了其结构.在溶液中结晶,获得了4个代表性化合物的单晶并进行X射线衍射分析,结果表明,3-苯基-12-取代环十二酮晶体中的十二元环仍采取[3333]-2-酮构象,2个取代基为反式构型,取代基存在2种情形:2个取代基在同一条边上,苯基位于与羰基间隔1个亚甲基的β-角碳反向位,而另1个取代基位于与羰基另一侧相邻的α-角碳顺向位;或2个取代基在2条边上,苯基位于与羰基间隔1个亚甲基另一条边的β-边碳外向位,而另1个取代基位于与羰基另一侧相邻并在同一条边的α-边碳外向位,量子力学计算结果与晶体衍射分析结果一致.     

Studies on the reaction of α-imino esters with organometallic compounds

Benzylzinc reagent reacted with α-imino ester (2) at the α-carbon exclusively, though other organometallic reagents such as Mg. Al, Cu, Tl, and B derivatives reacted at the nitrogen atom. Use of the (S)-amine as a chiral auxiliary of 2 created the R chirality at the imino carbon. Very high chiral Induction was realized In the reaction of prenylzinc reagent wlih α-imino 8-(-)phenylmenthyl ester (10). The reaction of 2 with heteroatom substituted allylic organometalic compounds (15) gave the corresponding α-heterostom substituted amino acid derivatives (16). Here again, the allylic zinc reagent gave the adduct in higher yield than the corresponding Tl, Al, and B reagents.     

Domino‐Hydroformylation/Aldol Condensation Catalysis: Highly Selective Synthesis of α,β‐Unsaturated Aldehydes from Olefins

A general and highly chemo‐, regio‐, and stereoselective synthesis of α,β‐unsaturated aldehydes by a domino hydroformylation/aldol condensation reaction has been developed. A variety of olefins and aromatic aldehydes were efficiently converted into various substituted α,β‐unsaturated aldehydes in good to excellent yields in the presence of a rhodium phosphine/acid–base catalyst system. In view of the easy availability of the substrates, the high atom‐efficiency, the excellent selectivity, and the mild conditions, this method is expected to complement current methodologies for the preparation of α,β‐unsaturated aldehydes.     

Block copolymers and telechelic oligomers by end group reaction of polymethacrylates

Block copolymers and telechelic oligomers bearing methacrylate moities were obtained by means of a new highly selective end group reaction. Starting from polymethacrylates that were prepared by radical polymerization in the presence of mercaptanes as chain transfer agents, the resulting ester end group linked to the terminal tertiary carbon atom of the polymer backbone can be either transesterified or saponified selectively. The selectivity of the end group reactions was determined by MALDI-TOF-mass spectrometry. Polymethacrylate-b-poly(ethylene oxide)-, polymethacrylate-b-poly(methacrylic acid)- and polymethacrylate-b-polysiloxane-b-polymethacrylate-copolymers as well as α,ω-dihydroxy- and α,ω-dicarboxy-telechelic polymethacrylates were prepared by applying end group transesterification or end group saponification.     

Chromatographic retention and thermodynamics of the adsorption of α-phenylcarboxylic acid enantiomers on a chiral stationary phase with a grafted antibiotic eremomycin: Effect of eluent pH

The effect of the pH of aqueous–ethanol mobile phases on the retention and adsorption thermodynamics of the optical isomers of several α-phenylcarboxylic acids on a chiral stationary phase “Nautilus-E” with a grafted antibiotic, eremomycin, was studied. It was determined that ionic interactions dominated in the retention of α-phenylcarboxylic acid enantiomers. It was revealed that the Nautilus-E adsorbent was most selective to acids, the adsorption of which is an enthalpy-controlled process. It was found that the nature of adsorption was changed by varying the eluent pH. The dissociation constants of α-phenylcarboxylic acids have been determined by chromatographic method in aqueous–ethanol solution. A statistical analysis of the phenomenon of enthalpy-entropy compensation was performed, and a manifestation of the false compensation effect was established. It was shown that the spatial configuration of the molecule and the presence of polar groups on a chiral carbon atom in its structure have a greater influence on the chiral recognition mechanism of acid enantiomers using the Nautilus-E CSP.     

铜〔Ⅱ)与咪唑及2-羰基丙酸水杨酰腙混配体配合物的合成、晶体结构及热分解研究

以2-碳基丙酸水杨酰腙、咪唑与五水硫酸铜在水中反应，首次制得混配体配合 物Cu(C10H8N2O4）（C3H4N2）（H2O）[C10H8N2O4^2-为2-羰基丙酸水杨酰腙负离子 ；C3H4N2为咪唑]，并在甲醇溶剂中培养出单晶．该单晶为深绿色，属单斜晶系， 空间群为P2（1）/c，晶胞参数a=1.50583(5)nm,b=1.08411(3)nm,c=0.94366(2)nm, α=90°，β=101.5583(11)°,γ=90°,V=1.50927(7)nm^3,Z=4,μ=1.479mm^-1, Dc=1.628Mg/m^3,F(000)=756.00,R=0.0340,ωR=0.0777,GOF=1.025。晶体测试结果 表明，配合物中Cu(Ⅱ)的配位数为5，处于四方锥配位环境，其中配体2—羰基丙酸 水杨酰腙的羧基以单齿配位．腙基上C≡N的N配位以及碳基(C≡0)的0配位，咪唑的 3位N参与了配位，这四个配位原子处于四方锥的锥底，另一个配位原子来自H20中 的0，它处于四方锥的锥顶．在晶胞中，除分子内存在氢键外，分子间也存在氢键 ．根据TG-DTG曲线研究了配合物的热分解过程，利用Kissinger公式计算了配合物 主要分解阶段的表观活化能．     

The synthesis of halogenated pyridines substituted at the carbon atom C-3

Arylation of α-methyleneglutaronitrile (MGN) occurred when arylamines, aminopyridines and 3-aminothiophene were treated with alkylnitrites and copper(I) chloride in dimethyl methylphosphonate (DMMP) solutions. Results from this study exemplified the synthetic advantage of DMMP as a solvent in Meerwein reactions with an olefin of low reactivity, yielding 1-aryl-2 chloro-2,4-dicyanobutanes, and its 3-pyridyl- and thiophen-3-yl analogues. Partial hydrolysis, followed by subsequent ring closure of the substituted 2,4-dicyanobutanes to 2,6-piperidinediones (glutaric acid imides) was effected with a solution of sulfuric acid in acetic acid. The aromatization of the substituted 2,6-piperidinediones with phosphorus oxychloride in the presence of hexamethylphosphoric acid triamide (HMPT) yielded the 2,6-dichloropyridine moiety substituted at the carbon atom C-3.