High-performance CE: an effective method to study lactonization of alpha2,8-linked oligosialic acid

A sensitive and efficient method using high-performance CE (HPCE) and neuraminidase hydrolysis was developed to study the lactonization and hydrolysis of alpha2,8-pentasialic acid. Eleven lactone species of pentasialic acid formed in glacial acetic acid were detected and classified into three groups based on the number of carboxylic acids: monolactones with four carboxylic acids, dilactones with three carboxylic acids, and trilactones with two carboxylic acids. These lactones eluted between the original pentamer (with five carboxylic acids) and the fully lactonized species (with one carboxylic acid) in HPCE. Eight of the isomers were identified by hydrolysis with neuraminodase. Results obtained from previous reports and from this study together reveal a general rule for predicting the subtle difference in the acidity of each carboxylic acid in oligosialic acids: the closer the carboxylic acid is to the nonreducing end, the more acidic it is. Therefore, the elution order of lactone isomers having the same number of carboxylic groups can be predicted from the position of the free carboxylic groups in pentasialic acid. We used this principle and the results of hydrolysis with neuraminidase to identify hexamer lactone isomers separated by HPCE.     

Improved alkylation and product stability in phosphotriester formation through quinone methide reactions with dialkyl phosphates

Investigating reactions of functionalized p-quinone methides continues to advance our design of a reagent being developed for controlled, in situ modification of DNA via phosphodiester alkylation. Previously reported investigations of p-quinone methides derived from catechols allowed for trapping of isolable trialkyl phosphates for characterization and mechanistic information. However, lactone formation with these derivatives required long reaction times, resulting in an unfavorable mixture of trialkyl phosphate and hydrolysis products. To enhance the rate and efficacy of trialkyl phosphate formation and trapping, a phenol derived p-quinone methide has been designed to enforce a conformation favoring lactonization of the dialkyl phosphate alkylated intermediate. The relative rates of phosphodiester alkylation and subsequent trapping of the phosphotriester adduct have been examined by UV and (1)H NMR analysis for p-quinone methide precursor 1 and the corresponding control, 1'. The incorporation of a methyl group at the meta-position of 1 (relative to 1') significantly improves the rate of lactionization to provide a much higher yield of the desired product, lactonized phosphotriester 5. The control reaction with 1' afforded only a minor amount of the corresponding lactonized trialkyl phosphate 5'.     

Synthesis of tumor-associated glycopeptide antigens for the development of tumor-selective vaccines

In contrast to normal cells, the glycoprotein profile on epithelial tumor cells is distinctly altered. Due to an incomplete formation of the glycan side-chains resulting from a premature sialylation, additional peptide epitopes become accessible to the immune system in mucin-type glycoproteins on tumor cells. These tumor-associated structure alterations constitute the basis for a selective immunological attack on cancer cells. For the construction of immunostimulating antigens, glycopeptide partial structures from the mucins MUC1 and MUC4 carrying the tumor-associated sialyl-T(N), alpha2,6-sialyl-T and alpha2,3-sialyl-T antigens have been synthesized. Employing different linkers such as the allylic HYCRON or the fluoride-sensitive PTMSEL anchor, the antigenic glycopeptide structures were constructed on the solid phase utilizing pre-assembled glycosyl amino acid building blocks prepared in solution by convergent chemical or chemoenzymatic strategies. The proliferation of cytotoxic T cells has been induced applying a construct composed of a sialyl-T(N) MUC1-glycopeptide conjugated with a tetanus toxin T cell peptide epitope.     

Synthetic Multivalent Glycopeptide‐Lipopeptide Antitumor Vaccines: Impact of the Cluster Effect on the Killing of Tumor Cells

Multivalent synthetic vaccines were obtained by solid‐phase synthesis of tumor‐associated MUC1 glycopeptide antigens and their coupling to a Pam₃Cys lipopeptide through click reactions. These vaccines elicited immune responses in mice without the use of any external adjuvant. The vaccine containing four copies of a MUC1 sialyl‐T_N antigen showed a significant cluster effect. It induced in mice prevailing IgG_2a antibodies, which bind to MCF‐7 breast tumor cells and initiate the killing of these tumor cells by activation of the complement‐dependent cytotoxicity complex.     

The chemistry of indole

A number of amides of indole ketoacids are synthesized. 3-Carboxyacylindoles can be converted to the corresponding enol-lactones by treatment with acetic anhydride or acetyl chloride. Reaction of the lactones with ammonia or amines involves lactone ring opening, and this makes it possible to prepare some N-substituted or unsubstituted ketoacid amides. Deacylation can occur in the action of strong bases or high temperatures on indoleketoacids. Reaction of 2-(indolyl-3') benzoic acid with dimethyl sulfate proceeds in two ways: the NH group is methylated, and there is conversion to the corresponding indolenine, with subsequent methylation of the enol.For Part II see [1].     

New anti-tumor agents. 1. Heterocyclic benzodioxole lactones

Morpholino Mannich bases of types 5, 12 react with tetronic acid in aqueous acetic acid to yield uncyclized lactones of types 7, 13 . Acetylation and methylation of these products yields monoacetyl-monomethyl derivatives which can then be cyclized in alkali to give unsaturated lactones of types 8, 16 and saturated lactones 9b, 15 . The hydroxylactone 9a can be synthesized directly by reaction of 3,4,5-trimethoxybenzaldehyde with sesamol and tetronic acid in methanol. With few exceptions the lactones of type 8 and 16 have proven to be active inhibitors of tumor growth in the National Cancer Institute in vitro screening program against 60 diverse human cancer cell lines. The lactone 8 is particularly potent, inhibiting in vitro growth of some cancers at concentrations as low as 10^?6-10^?7 moles/1.     

Hydroxymethylphenylnaphthoie acid lactones

Reduction of 1-phenylnaphthalene-2,3-dicarboxylic anhydride (I) with zinc and acetic acid or lithium aluminium hydride yields a mixture of 1-phenyl-3-hydroxymethyl-2-naphthoie acid lactone (II) and 1-phonyl-2-hydroxymethyl-3-naphthoie acid lactone (III). Catalytic hydrogenation of (I) gave the tetrahydronaphthalene dicarboxylic anhydride (IV). Oxidation of the phenyldihydronaphthofuran (X), prepared by base-catalyzed cyclization of the ether (IX), also yielded lactones (II) and (III). The phenyltetrahydronaphthofuran (XII) was similarly prepared by cyclization of the phenylpropargyl cinnamyl ether (XI).     

酶法动力学拆分制备光学活性γ-内酯

研究了脂肪酶对桃醛和γ-癸内酯的水解动力学拆分反应,考察了温度、pH值、酶的用量等因素对酶催化水解拆分过程的影响.选择氯化钙-阿拉伯胶水溶液作为反应介质,使γ-内酯拆分产物取得较高的ee值.回收拆分中产生的γ-羟基酸,外消旋化后再内酯化,投入下一批反应,提高了光学活性γ-内酯的总得率.     

Lactone enols are stable in the gas phase but highly unstable in solution

2-Hydroxyoxol-2-ene (C(5)-1), the enol tautomer of gamma-butyrolactone, was generated in the gas phase as the first representative of the hitherto elusive class of lactone enols and shown by neutralization-reionization mass spectrometry to be remarkably stable as an isolated species. Ab initio calculations by QCISD(T)/6-311+G(3df,2p) provided the enthalpies of formation, proton affinities, and gas-phase basicities for gaseous lactone enols with four- (C(4)-1), five- (C(5)-1), and six-membered rings (C(6)-1). The acid-base properties of C(4)-C(6) lactones and enols and reference carboxylic acid enols CH(2)=C(OH)(2) (3) and CH(2)=C(OH)OCH(3) (4) were also calculated in aqueous solution. The C(4)-C(6) lactone enols show gas-phase proton affinities in the range of 933-944 kJ mol(-)(1) and acidities in the range of 1401-1458 kJ mol(-)(1). In aqueous solution, the lactone enols are 15-20 orders of magnitude more acidic than the corresponding lactones, with enol pK(a) values increasing from 5.6 (C(4)-1) to 14.5 (C(6)-1). Lactone enols are moderately weak bases in water with pK(BH) in the range of 3.9-8.1, whereas the lactones are extremely weak bases of pK(BH) in the range of -10.5 to -17.4. The acid-base properties of lactone enols point to their high reactivity in protic solvents and explain why no lactone enols have been detected thus far in solution studies.     

Kiliani on ketoses: branched carbohydrate building blocks from d-fructose and l-sorbose

Protected branched sugar lactones are available via Kiliani-acetonation sequences on readily available ketoses such as d-fructose and l-sorbose. In both cases, the readily crystallized diacetonides have a 2,3-cis-diol relationship in the product lactone. An efficient double inversion of the configuration at C-4 and C-5 of the product from d-fructose gives access to the formal Kiliani product from l-psicose. Branched carbohydrate lactones are likely to be of significant value as chirons for homochiral targets with functionalized quaternary centres.     

Hydroxy lactones with the gem-dimethylcyclohexane system – Synthesis and antimicrobial activity

Two new lactones comprising the gem-dimethylcyclohexane ring: 2-chloro-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one and 2-bromo-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one as well as the already known 2-iodo-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, were obtained from (6,6-dimethylcyclohex-2-en-1-yl)acetic acid. These lactones were used as substrates for the screening of biotransformation by whole cells of nine fungal strains (Fusarium species, Syncephalastrum racemosum and Cunninghamella japonica). Some of these microorganisms (mainly Fusarium species) transformed all three lactones during the hydrolytic dehalogenation into 2-hydroxy-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one. It is worth noting that two microorganisms (Fusarium culmorum and Fusarium scirpi) converted iodolactone with very high enantioselectivity (75.1% and 91.6%, respectively). The (+) isomer of hydroxy lactone was preferred. At the last step the hydroxy lactone obtained during biotransformation was examined for its biological activity against bacteria, yeasts and fungi. It was found that this compound inhibits growth of some tested microorganisms.     

Chemoenzymatic synthesis of sialylated glycopeptides derived from mucins and T-cell stimulating peptides.

The Tn, T, sialyl-Tn, and 2,3-sialyl-T antigens are tumor-associated carbohydrate antigens expressed on mucins in epithelial cancers, such as those affecting the breast, ovary, stomach, and colon. Glycopeptides carrying these antigens are of interest for development of cancer vaccines and a short, chemoenzymatic strategy for their synthesis is reported. Building blocks corresponding to the Tn (GalNAc alpha-Ser/Thr) and T [Gal beta(1-->3)GalNAc alpha-Ser/Thr] antigens, which are relatively easy to obtain by chemical synthesis, were prepared and then used in the synthesis of glycopeptides on the solid phase. Introduction of sialic acid to give the sialyl-Tn [Neu5Ac alpha(2-->6)GalNAc alpha-Ser/Thr] and 2,3-sialyl-T [Neu5Ac alpha(2-->3)Gal beta(1-->3)GalNAc alpha-Ser/Thr] antigens is difficult when performed chemically at the building block level. Sialylation was therefore carried out with recombinant sialyltransferases in solution after cleavage of the Tn and T glycopeptides from the solid phase. In the same manner, the core 2 trisaccharide [Gal beta 1-->3(GlcNAc beta 1-->6)GalNAc] was incorporated in glycopeptides containing the T antigen by using a recombinant N-acetylglucosaminyltransferase. The outlined chemoenzymatic approach was applied to glycopeptides from the tandem repeat domain of the mucin MUC1, as well as to neoglycosylated derivatives of a T cell stimulating viral peptide.     

New triterpene diglycosides from the rhizome of Cimifuga foetida

Five new 9,19-cycloartane triterpene diglycosides, which have been named cimiaceroside C (1), and cimifosides A-D (2-5) together with the known compounds cimiracemoside D (6), cimidahurine (7) and alpha-D-glucopyranosyl-l-beta-D-fructofuranoside (8) were isolated from the rhizome of Cimicifuga foetida. The new triterpene diglycosides 1-5 were identified as cimiacerol-3-O-beta-D-xylopyranosyl-(1'-->3')-beta-D-xylopyranoside, 12beta-hydroxycimigenol-3-O-beta-D-xylopyranosyl-(1'-->3')-beta-D-xylopyranoside, 25-Oacetylcimig-enol-3-O-beta-D-xylopyranosyl-(1'-->3')-beta-D-xylopyranoside, 24- acetylhydroshengmanol-3-O-beta-D-xylopyranosyl-(1'-->3')-beta-D-xylopyranoside and 26-deoxyacetylacteol-3-O-beta-D-xylo- pyranosyl-(1'-->3')-beta-D-xylopyranoside, respectively, based on analysis of their spectral data and chemical reactions.     

在冰醋酸溶液中L(+)-伪麻黄碱的异构化

在冰醋酸溶液中,L(+)-伪麻黄碱可以异构化成D(-)-麻黄碱。氧化铝薄层层析结果表明:在反应液中存在N-乙酰L(+)-伪麻黄碱,N-乙酰D(-)-麻黄碱和一种未鉴定结构的化合物,并初步推出可能的异构化机理。5-10％L(+)-伪麻黄碱的冰醋酸溶液,回流反应20小时,立即回收醋酸后,用2.5/V的氢氧化钠溶液进行水解,再通过草酸盐变为盐酸盐即得。以L(+)-伪麻黄碱计纯盐酸D(-)-麻黄碱收率达31.2％。     

Phenolic glycosides from Lindera fruticosa root and their inhibitory activity on osteoclast differentiation

Two new compounds were found in the phenolic glycosides isolated from the roots of Lindera fruticosa: 5-O-[beta-D-apiofuranosyl-(1'-->2')-O-beta-D-xylopyranosyl]gentisic acid-7,5'-ester (3), named linderofruticoside A; and 5-O-[beta-D-apiofuranosyl-(1'-->3')-O-beta-D-xylopyranosyl]gentisic acid methyl ester (4), linderofruticoside B. Two previously known phenolic glycosides were also identified: beta-D-(3,4-disinapoyl)fructofuranosyl-alpha-D-(6-sinapoyl)glucopyranoside (1) and beta-D-(3-sinapoyl)fructofuranosyl-alpha-D-(6-sinapoyl)glucopyranoside (2). Compounds 1 and 2 inhibited osteoclast differentiation in a dose-dependent manner at concentrations higher than 1.04 microM and 0.132 microM, respectively.     

A New Synthesis of 3-Chloro Butenolides via Rearrangement of 3,3-Dichloro Beta Lactones

4,4-Dialkyl 3,3-dichloro oxetan-2-ones rearrange under Lewis acid catalysis, accompanied by loss of HC1, to afford 4,5-dialkyl 3-chloro butenolides.

We have recently been investigating the reactions of beta lactones under the influence of Lewis acid catalysis.¹ When the lactone ring oxygen is bonded to a secondary carbon atom, a rearrangement occurs in which the beta lactone 1 expands to a butyrolactone 4 with the concommitant migration of a hydrogen or carbon atom into the lactone ring.² If the oxygen is bonded to a tertiary carbon, an ionization/elimination sequence ensues, producing a β, γ-unsaturated carboxylic acid     

肾上腺素电氧化生成肾上腺素醌的反应动力学

使用以铂片为工作电极的长光程薄层电化学池,采用单电位阶跃计时吸收法测定了1．0mol·L^-1H2SO4和冰醋酸中,肾上腺素电氧化生成肾上腺素醌的动力学参数．实验结果表明：肾上腺素在1．0mol·L^-1H2SO4介质中比在冰醋酸中容易被氧化．     

A Fully Synthetic Four‐Component Antitumor Vaccine Consisting of a Mucin Glycopeptide Antigen Combined with Three Different T‐Helper‐Cell Epitopes

In a new concept of fully synthetic vaccines, the role of T‐helper cells is emphasized. Here, a synthetic antitumor vaccine consisting of a diglycosylated tumor‐associated MUC1 glycopeptide as the B‐cell epitope was covalently cross‐linked with three different T‐helper‐cell epitopes via squaric acid ligation of two linear (glyco)peptides. In mice this four‐component vaccine administered without external immune‐stimulating promoters elicit titers of MUC1‐specific antibodies that were about eight times higher than those induced by a vaccine containing only one T‐helper‐cell epitope. The promising results indicate that multiple activation of different T‐helper cells is useful for applications in which increased immunogenicity is required. In personalized medicine, in particular, this flexible construction of a vaccine can serve as a role model, for example, when T‐helper‐cell epitopes are needed that match human leukocyte antigens (HLA) in different patients.     

A general synthesis of substituted indoles from cyclic enol ethers and enol lactones

[reaction: see text] X = CH2, C[double bond]O, R2 = H, alkyl. A general method was developed for the one-pot synthesis of highly functionalized indoles from simple, commercially available aryl hydrazines and cyclic enol ethers. Enol lactones were also used as substrates, affording substituted indole acetic acid or indole propionic acid derivatives. This procedure affords 2,3-disubstituted indoles as single regioisomers from the appropriately substituted enol ether or enol lactone. This method was highlighted in the efficient synthesis of the antimigraine drug sumitriptan and the antiinflammatory drug indomethacin.     

Liquid Chromatographic Determination of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase Inhibitors

Reversed-phase high-performance liquid chromatography (RP-HPLC) was used as a tool to explore the retention behavior and separation of four 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, namely compactin, lovastatin, simvastatin, and pravastatin in their hydroxy acid and lactone forms. The contribution of C-6 and C-2′ methyl groups and lactonization to the molecular hydrophobicity among these four structurally related HMG-CoA reductase inhibitors were elucidated. Eight components (four lactones and four hydroxy acids) could be resolved by RP-HPLC with isocratic elution. In a binary mobile phase system of acetonitrile-water containing 0.5% acetic acid, the free hydroxy acids and corresponding lactone forms remained intact and were completely separated. This study demonstrated that RP-HPLC is suitable for simultaneous determination of active and prodrug forms of these HMG-CoA reductase inhibitors.