Synthesis of bicyclic tertiary alpha-amino acids

Novel bicyclic alpha-amino acids, exo and endo-1-azabicyclo[2.2.1]heptane-2-carboxylic acid, 1-azabicyclo[2.2.1]heptane-7-carboxylic acid, and 1-azabicyclo[3.2.2]nonane-2-carboxylic acid have been readily synthesized for the generation of neuronal nicotinic receptor ligands. Alkylation of glycine-derived Schiff bases or nitroacetates with cyclic ether electrophiles, followed by acid-induced ring opening and cyclization in NH4OH, allowed for the preparation of substantial quantities of the three tertiary bicyclic alpha-amino acids.     

Synthesis and reactions of fluorous carbobenzyloxy (FCbz) derivatives of alpha-amino acids

Fluorous carbobenzyloxy ((F)Cbz) reagents RfCH(2)CH(2)C(6)H(4)CH(2)OC(O)OSu (where Su is succinimidoyl and Rf is C(6)F(13) and C(8)F(17)) have been used to make (F)Cbz derivatives of 18 of the 20 natural amino acids. The potential utility of this new family of reagents in both standard fluorous synthesis with spe separation and fluorous quasiracemic synthesis is illustrated with representative reactions of the (F)Cbz-Phe derivatives.     

Synthesis of peptides based onβ-(N1-uracilyl)-α-alanine

The synthesis of peptides which include a DL--(N₁-uracilyl)--alanine (DL-willardiine) residue as an N-terminal or C-terminal group was investigated, dipeptides of DL-willardiine with glycine and L-tyrosine were obtained, and DL-willardiyl-DL-willardiine was synthesized; the latter is the simplest representative of the family of monotonic homopeptides which contain, as a repeating side substituent, a natural nucleic base capable of participation in intermolecular interactions of the complementary type.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 404–408, March, 1971.     

Versatile synthons for optically pure alpha-amino aldehydes and alpha-amino acids: (+)- and (-)-4,5-dialkoxy-2-oxazolidinones

Both enantiomers of trans-5-benzyloxy-4-methoxy- (BMOx) and trans-4,5-dimethoxy-2-oxazolidinones (DMOx), which are readily accessible from simple 2-oxazolone heterocycles, represent good candidates for a new class of chiral synthons for use in the preparation of optically pure alpha-amino aldehydes and alpha-amino acids, respectively.     

Synthesis of N-hydroxysuccinimide esters of N-protected amino acids and peptides using N,N′-disuccinimidyl sulfite

Conclusions A method was proposed for the preparation of N,N-disuccinimidyl sulfite, a new efficient reagent for the synthesis of the N-hydroxysuccinimide esters of N-protected amino acids and peptides, which consists in treating N-trimethylsiloxysuccinimide with thionyl chloride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1163–1165, May, 1984.     

Synthesis of peptides from β- (1-pyrimidyl)-and β- (9-purinyl)-α-amino acids

The activated ether and dicyclohexylcarbodiimide methods were used to obtain di- and tripeptides of -(1-thyminyl)--alanine and -(9-adenyl)--alanine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 705–707, May, 1972.     

Synthesis of (-)-quinocarcin by directed condensation of alpha-amino aldehydes

An enantioselective synthesis of the natural antiproliferative agent quinocarcin was achieved by the directed condensation of optically active alpha-amino aldehyde intermediates. Condensation of the N-protected alpha-amino aldehyde 1, prepared in eight steps (19% yield) from (R,R)-pseudoephedrine glycinamide, with the C-protected alpha-amino aldehyde derivative 2, prepared in seven steps (34% yield) from (R,R)-pseudoephedrine glycinamide, afforded the corresponding imine in quantitative yield. Without isolation, direct treatment of this imine intermediate with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and hydrogen cyanide led to cleavage of the fluorenylmethoxycarbonyl (Fmoc) protective group followed by addition of cyanide (Strecker reaction) to form the bis-amino nitriles 3 as a mixture of diastereomers, in 91% yield. Treatment of the diastereomers 3 with trimethylsilyl cyanide and zinc chloride in 2,2,2-trifluoroethanol at 60 degrees C led to stepwise cyclization to form the tetracyclic product 4 (42% yield from 1 and 2). The latter intermediate was transformed into (-)-quinocarcin (1) in five steps (45% yield). The yield of quinocarcin was 19% from 1 and 2 (7 steps), and 4% from pseudoephedrine glycinamide (15 steps).     

Synthesis of cyclopropene alpha-amino acids via enantioselective desymmetrization

[reaction: see text] The preparation of cyclopropene alpha-amino acids via the enantioselective desymmetrization of cyclopropene bis-carboxylic acid derivatives is described. The amino acids are stable to harsh reaction conditions, and a derivative has been incorporated into a tripeptide using conventional methods for peptide synthesis.     

Syntheses of thyrotropin-releasing hormones (TRH) (Schaf) and related peptides

The syntheses of seven tripeptide isomers containing L -histidine, L -proline and L -glutamic acid residues, the same as found in the natural thyrotropin-releasing hormone (TRH), are reported. In addition L -pyroglutamyl-L -histidyl-L -proline and its amide as well as N^α-acetyl-L -glutamyl-L -histidyl-L -proline are described. Whereas eight peptides are inactive and L -pyroglutamyl-L -histidyl-L -proline shows a slight TRH activity, L -pyroglutamyl-L -histidyl-L -proline-amide has the full biological activity of the isolated thyrotropin-releasing hormone and, at the present state of knowledge, seems to be identical with it.     

Covalently bonded platinum(II) complexes of alpha-amino acids and peptides as a potential tool for protein labeling

Arylplatinum(II) complexes have been covalently bonded to the N and C termini and to the alpha-carbon of various amino acid derivatives. These organometallic-functionalized amino acid compounds can be converted into the corresponding free amino acids under both basic and acidic conditions; this demonstrates the excellent stability properties of these biomolecules. Due to the NMR activity displayed by the 195Pt nucleus (natural abundance 33.8%, I = 1/2) these compounds are functional bio-markers. Furthermore, the ability of the arylplatinum functional group to bind SO2 gas, selectively and reversibly as indicated by changes in the spectroscopic properties (1H, 13C, 195Pt NMR and UV spectra) of these compounds, allows for the potential use of these complexes as in vitro biosensors.     

Sterically hindered C(alpha, alpha)-disubstituted alpha-amino acids: synthesis from alpha-nitroacetate and incorporation into peptides

The preparation of sterically hindered and polyfunctional C(alpha,alpha)-disubstituted alpha-amino acids (alpha alpha AAs) via alkylation of ethyl nitroacetate and transformation into derivatives ready for incorporation into peptides are described. Treatment of ethyl nitroacetate with N,N-diisopropylethylamine (DIEA) in the presence of a catalytic amount of tetraalkylammonium salt, followed by the addition of an activated alkyl halide or Michael acceptor, gives the doubly C-alkylated product in good to excellent yields. Selective nitro reduction with Zn in acetic acid or hydrogen over Raney Ni gives the corresponding amino ester that, upon saponification, can be protected with the fluorenylmethyloxycarbonyl (Fmoc) group. The first synthesis of an orthogonally protected, tetrafunctional C(alpha,alpha)-disubstituted analogue of aspartic acid, 2,2-bis(tert-butylcarboxymethyl)glycine (Bcmg), is described. Also, the sterically demanding C(alpha,alpha)-dibenzylglycine (Dbg) has been incorporated into a peptide using solid-phase synthesis. It was found that once sterically congested Dbg is at the peptide N-terminus, further chain extension becomes very difficult using uronium or phosphonium salts (PyAOP, PyAOP/HOAt, HATU). However, preformed amino acid symmetrical anhydride couples to N-terminal Dbg in almost quantitative yield in nonpolar solvent (dichloroethane-DMF, 9:1).     

1,4,7,10-N,N,N,N.四(2-(4-(2-乙酰硫基乙氧基)苯氧基)乙基)-1,4,7,10-四氮杂环十二烷的合成研究

以对苄氧基苯酚为原料,经3步反应合成不对称的对苯二酚烷氧基化合物,并以此为原料,合成乙酰硫基修饰的cyclen四取代氢醌醚链化合物.该路线不仅反应条件温和,操作易行,且收率高,克服了文献报道的合成路线重复性差、收率低的缺点.关键中间体及目标化合物经~1H NMR、~(13)C NMR、MS、IR和元素分析表征.     

First practical protection of alpha-amino acids as N,N-benzyloxycarbamoyl derivatives

The consecutive treatment of N-Cbz amino protected compounds with LiHMDS and CbzCl provides a practical method for the preparation of N,N-benzyloxycarbamoyl (N,N-di-Cbz) derivatives in good yield. When alpha-amino acids are used the protection occurs without racemization. The method is compatible with a wide range of other functional and protecting groups. The procedure is also valid for the synthesis of mixed N,N-carbamoyl derivatives.     

A new strategy to induce gamma-turns: peptides composed of alternating alpha-aminoxy acids and alpha-amino acids

It is known that the seven-membered-ring intramolecular hydrogen bond (gamma-turn) is seldom formed in naturally occurring peptides composed of alpha-amino acids. Here we report a new strategy to induce gamma-turns in short linear peptides. We designed and synthesized several peptides (1-5) containing alternating alpha-l-aminoxy acids and alpha-d-amino acids. 1H NMR studies revealed that the gamma-turn could be initiated by the following N-O turn, an eight-membered-ring intramolecular hydrogen bond induced by an alpha-aminoxy acid. Moreover, NOESY and CD studies suggested peptides 4 and 5 form a novel secondary structure, a mixed 7-8 helix. Theoretical calculations on several di-, tri-, and tetrapeptide models provided strong support to the above conclusions.     

螯合金属离子亲和色谱法分离α-氨基酸和肽

 以ＳｅｐｈａｄｅｘＧ１０为基质螯合二价铜离子的亲和色谱法分离α－氨基酸和肽，使之得以完全分离。对分离过程的原理进行了讨论。     

New insulinomimetic zinc(II) complexes of alpha-amino acids and their derivatives with Zn(N2O2) coordination mode

Zinc(II) complexes of alpha-amino acids and their derivatives with a Zn(N2O2) coordination mode were found to have in vitro insulinomimetic activity as estimated with the inhibition of free fatty acid release in isolated rat adipocytes treated with epinephrine. It was revealed that the insulinomimetic activities of zinc(II) complexes with over-all stability constants (log beta) less than 10.5 are higher than those of ZnSO4 and VOSO4. The high blood glucose level of KK-Ay mice with type 2 diabetes mellitus was lowered by daily intraperitoneal injections of a zinc(II) complex, cis-[Zn(L-Thr)2(H2O)2], for 14 d. The improvement of diabetes mellitus was confirmed with the oral glucose tolerance test.     

Synthesis of alpha-amino acids by reaction of aziridine-2-carboxylic acids with carbon nucleophiles

A variety of homochiral alpha-amino acids have been prepared in good yield via regioselective reaction of higher order cuprates with (2S)-N-para-toluenesulfonylaziridine-2-carboxylic acid 4. The reaction was much less regioselective and low yielding when higher order cuprates were reacted with the more hindered aziridine carboxylic acid 30, the principal products being protected beta-amino acids. Reaction of lithium trimethylsilylacetylide with the aziridine acid 30, however, gave a protected alpha-amino acid which was converted to the protected isoleucine ester 37.     

Enantioselective benzoylation of alpha-amino esters using (S)-1-benzoyl-2- (alpha-acetoxyethyl)benzimidazole, a chiral benzimidazolide

A new chiral benzimidazolide is developed as a nonenzymatic acylating agent for enantioselective benzoylation of racemic alpha-amino esters. The process is highly efficient, which exhibits uniformly high enantioselectivity for alpha-amino esters with or without aryl substituents under mild reaction conditions. The chiral benzimidazolide is inexpensive and is easily accessible.