Microwave-assisted direct esterification of a cyclic phosphinic acid with phenols

1. Download high-res image (92KB)
2. Download full-size image

     

Preparative scale purification of shidasterone, 2-deoxy-polypodine b and 9a,20-dihydroxyecdysone from Silene italica ssp. nemoralis

A suitable combination of preparative scale separation methods results in effective clean-up of the ecdysteroids of Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman. The isolation of minor ecdysteroids from the partially purified extract is based on the use of both droplet counter-current chromatography and low-pressure reversed-phase liquid chromatography. The purification is completed by preparative thin-layer chromatography and preparative high-performance liquid chromatography to obtain the minor ecdysteroids, such as 2-deoxy-20-hydroxyecdysone, shidasterone, 2-deoxy-polypodine B, makisterone C, and 9alpha,20-dihydroxyecdysone.     

Synthesis and conformational analysis of 1,3,2-diazaphosphorino[6,1-a]isoquinolines, a new ring system

Through ring-closure reactions of N- or 1′-substituted 1-(2′-aminoethyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines (5a-e) with phenylphosphonyl dichloride, 1- or 3-substituted 4-phenyl-1,3,4,6,7,11b-tetrahydro-2H-1,3,2-diazaphosphorino[6,1-a]isoquinolin-4-one diastereomers (7a-e and 8a-c,e), the first representatives of a new ring system, were prepared. The diastereomeric ratios in the cyclizations and the conformer (A-E) populations of the nitrogen-bridged tricyclic systems (7 and 8) were strongly influenced by the N- and 1′-substituents of the starting diamines. The conformational analysis of compounds 7 and 8 was performed by ¹H, ¹³C and ³¹P NMR methods.     

Reaction of substituted furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with hippuric acid

4-Heteroarylidene-2-phenyl-1,3-oxazol-5(4H)-ones were prepared by reactions of hippuric acid with substituted furan-2-carboxaldehydes or furo[b]pyrrole type aldehydes. The reactivity of various furan-2-carboxaldehyde derivatives in this reaction is discussed. The effect of microwave irradiation on some condensation reactions was compared with "classical" conditions. The results show that microwave irradiation shortens the reaction times while affording comparable yields. Elementary analysis, UV, IR and 1D NMR proved the structure of new synthesised compounds. 2D NMR spectroscopic measurements confirmed that the configuration at the carbon-carbon double bond corresponds to the pure E isomers of the products.     

Superoxide dismutase mimicking Cu(II)–mixed amino acid complexes covalently grafted onto silica gel—an FT-IR study

Our recent work concerning the synthesis, characterisation and testing of bioinspired electron transfer catalysts is described in this contribution. The catalysts were various Cu(II) complexes having mixed C- or N-protected amino acids (l-histidine and l-tyrosine) as ligands covalently grafted onto surface-modified silica gel. The resulting materials were structurally characterised by FT-IR spectroscopy, and their superoxide dismutase activities were tested. The covalently anchored Cu(II) complexes displayed appreciable activities in the test reaction; thus, they may be considered as promising candidates as durable electron transfer catalysts approaching the efficiency of the enzyme mimicked.     

The invariance of the arithmetic mean with respect to generalized quasi-arithmetic means

The aim of this paper is to find those pairs of generalized quasi-arithmetic means on an open real interval I for which the arithmetic mean is invariant, i.e., to characterize those continuous strictly monotone functions φ,ψ:I→R and Borel probability measures μ,ν on the interval [0,1] such that

     

Electron ionization mass spectra of phosphorus-containing heterocycles. I. 1,4,4a,5,6,7,8,8a-octahydro-2H-3,1,2-benzoxazaphosphinine 2-oxides

The electron ionization mass spectra of 27 cis- and trans-annelated 1,4,4a,5,6,7,8,8a-octahydro-2H-3,1,2-benzoxazaphosphinine 2-oxides were recorded to clarify the effects of the ring heteroatom (O or N), ring annelation, the P configuration and the substituents attached to the ring or to the N and P atoms. For compounds 1-12 different alkyl radical and alkene losses and the cleavage of the P-heteroatom bonds, instead of the P-C bonds, were representative and dependent mainly on the substitution on the N and P atoms. The replacement of Ph and OPh by N(CH2CH2Cl)2 on the P atom had a dramatic influence on the fragmentation process: new fragment ions were obtained and very little M+ (1-3%) was formed. Only slight differences were found between some of the corresponding isomers, but interestingly the compounds formed clear groups on the basis of the differences in their fragmentation, depending on the ring-N and ring-P substituents.     

On the Lipschitz perturbation of monotonic functions

Summary A real valued function <InlineEquation ID=IE"5"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"6"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"7"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"8"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"9"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"10"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"11"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"12"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"13"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"14"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"15"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"16"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"17"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"18"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"19"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"20"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"21"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"22"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"23"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"24"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"25"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"26"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"27"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"28"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"29"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"30"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"31"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"32"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"33"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"34"><EquationSource Format="TEX"><![CDATA[$]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>f$ defined on a real interval $I$ is called \emph{$d$-Lipschitz} if it satisfies $|\ell(x)- \ell(y)| \le d(x,y)$ for $x,y\in I$. In this paper, we investigate when a function $p\: I \to \bR$ can be decomposed in the form $p=q+ \ell$, where $q$ is increasing and $\ell$ is $d$-Lipschitz. In the general case when $d\: I^{2} \to \bR$ is an arbitrary semimetric, a function $p\: I \to \bR$ can be written in the form $p=q+ \ell$ if and only if \vspace{-4pt} <InlineEquation ID=IE"1"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"2"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"3"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"4"><EquationSource Format="TEX"><![CDATA[$$]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation> \sum_{i=1}^{n}{\big(p(s_{i})-p(t_{i})-d(t_{i},s_{i}) \big)^{+}} \le \sum_{j=1}^{m}{\big(p(v_{j})-p(u_{j})+d(u_{j},v_{j}) \big)} \vspace{-4pt} $$ is fulfilled for all real numbers $t_{1}<s_{1}, \dots, t_{n}<s_{n}$ and $u_{1}<v_{1}, \dots, u_{m}<v_{m}$ in $I$ satisfying the condition \vspace{-4pt} $$ \sum_{i=1}^{n} 1_{\left]t_i,s_i\right]}= \sum_{j=1}^{m} 1_{\left]u_j,v_j\right]}, \vspace{-4pt} $$ where $1_{\left]a,b\right]}$ denotes the characteristic function of the interval $\left]a,b\right]$. In the particular case when $d\: I^{2} \to R$ is a so-called concave semimetric, a function $p\: I \to \bR$ is of the form $p=q+ \ell$ if and only if \vspace{-4pt} $$ 0 \le \sum_{k=1}^{n}{d(x_{2k-1},x_{2k})} + d(x_0,x_{2n+1}) + \sum_{k=0}^{n}{\big(p(x_{2k+1})-p(x_{2k})\big)} \vspace{-4pt} $$ holds for all $x_0\le x_1\ki \cdots\ki x_{2n}\le x_{2n+1}$ in $I$.