New Routes to β-Iminophosphonates,Phosphineoxides, and Sulfides

Abstract

Two synthetic methods leading to β-iminophosphonates, phosphineoxides, and sulfides 2 are reported. The first method involves the reaction of imines with chlorophosphines and phosphites followed by oxidation or sulfurization. The second one utilizes the reaction of imines with diethylchlorophosphate and thiophosphate. The stereochemistry of the obtained products is discussed, and their structure is confirmed by NMR (¹H, ³¹P, ¹³C) and IR spectroscopies, and by mass spectrometry.

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GRAPHICAL ABSTRACT      

Author Index to Volume 24, 2006

ALI,A.,1 547ALI,Syed Mashhood,665AN,Yu,401;1 375AN,Zhong·Wei,1 754ANBIA,Mansur,1026AO,Li一Mei,253ASMAT)Fahmeena,665ATAV,Ulfet,603BAI,Chen一Xi,1 639BAI,Ji·Hai,360BAI,Zhu,1 24BALUJA,ShiPra,1327BAO,Han,481BAO,Hua一Ying,355BAO,Ren一Lie,1 001BAO,Xiao一Ling,85BERNATH,G巨bor,1792Bl,Cai一Feng,371B IAN,Liu一Jiao,653BLECHERT,Siegfried,1080BOKROS,Attila,1792CHANG,Jia一Zhong,1255CHANG,Lih一Wei,1238CHANG,Li·Qun,1 214CHEN,Bao一Quan,99CHEN,Bing,463CH…     

A new approach to δ-lactones,related to the Prelog-Djerassi lactone.

The reductive rearrangement of 2-ethoxy-5-(2-alkenyl)-2H-tetrahydropyrane systems, in the presence of AlBu¹₃, was used as the key-step in the synthesis of Prelog-Djerassi related lactones.     

A Facile,Sequential Multicomponent Approach to N-Aminoamidinothioureas—Versatile Synthons to Bioactive Heterocycles

A sequential, three-component approach for the rapid and convenient one-pot synthesis of N-aminoamidinothioureas is reported. The improved synthetic strategy involves the selective blocking of amino functionality in aminoguanidine by Schiff base formation with carbonyl compounds to generate corresponding N-(alkylidene/arylidene)aminoguanidines and their subsequent in situ condensation with isothiocyanate. The structural motif incorporates three points for diversity multiplication, making it a suitable candidate for combinatorial synthesis. The generality of the improved procedure was established by synthesizing a series of diverse compounds through solution phase parallel synthesis by varying the carbonyl and isothiocyanate components. The newly synthesized compounds were characterized by spectral methods. The developed synthetic procedure employs mild reaction conditions, and individual steps are carefully optimized for easy automation.     

Conjugate Addition of Alkyllithium Reagents to α,β-Unsaturated N,N',N'-Trimethylhydrazides

The site of nucleophilic attack by an alkyllithium reagent upon an α,β-unsaturated carbonyl compound is governed by, among other factors, the nature of the group attached to the carbonyl.¹ Thus the amount of carbonyl addition decreases in favor of conjugate addition for the α,β-unsaturated series: aldehyde, ketone, ester, amide. We wish to report that α,β-unsaturated carboxylic acid trimethylhydrazides, which have an exceptionally unreactive carbonyl group², undergo exclusive conjugate addition with simple alkyllithium reagents.³ Furthermore, the derived hydrazide lithium enolates can be transformed in convenient and useful ways.     

Synthetic Approaches to α-, β-, γ-, and δ-Lycoranes

Lycorane is a pentacyclic core presented in alkaloids isolated from the Amaryllidaceae family of herbaceous flowering plants. Members of this class of natural products have shown to display important biological properties including analgesic, antiviral, and antiproliferative activities. This review presents the known synthetic routes toward α-, β-, γ-, and δ-lycoranes. α-(19 routes), β-(10 routes), γ-(38 routes), and δ-(6 routes).     

Peptide binding to β-cyclodextrins: structure, dynamics, energetics, and electronic effects

Peptide-cyclodextrin and protein-cyclodextrin host-guest complexes are becoming more and more important for industrial applications, in particular in the fields of pharmaceutical and food chemistry. They have already deserved many experimental investigations although the effect of complex formation in terms of peptide (or protein) structure is not well-known yet. Theoretical calculations represent a unique tool to analyze such effects, and with this aim we have carried out in the present investigation molecular dynamics simulations and combined quantum mechanics-molecular mechanics calculations. We have studied complexes formed between the model Ace-Phe-Nme peptide and the β-cyclodextrin (β-CD) macromolecule, and our analysis focuses on the following points: (1) how is the peptide structure modified in going from bulk water to CD environment (backbone torsion angles), (2) which are the main peptide-CD interactions, in particular in terms of hydrogen bonds, (3) which relative peptide-CD orientation is preferred and which are the structural and energetic differences between them, and (4) how the electronic properties of the peptide changes under complex formation. Overall, our calculations show that in the most stable configuration, the backbone chain lies in the narrow rim of the CD. Strong hydrogen bonds form between the H atoms of the peptidic NH groups and oxygen atoms of the secondary OH groups in the CD. These and other (weaker) hydrogen bonds formed by the carbonyl groups reduce considerably the flexibility of the peptide structure, compared to bulk water, and produce a marked increase of the local dipole moment by favoring configurations in which the two C═O bonds point toward the same direction. This effect might have important consequences in terms of the peptide secondary structure, although this hypothesis needs to be tested using larger peptide models.     

Four‐Component Cyclocondensation of Aminodiazines,Glyoxal, Formaldehyde,and Methanol to Imidazolidines

Four‐component reaction of aminodiazines (2‐aminopyrimidine and 2‐aminopyrazine), glyoxal, formaldehyde, and methanol yields trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrimidinyl)imidazolidine (5a) and trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrazinyl)imidazolidine (5b), respectively. Changing methanol to acetonitrile leads to the formation of the corresponding 1,3‐bis(2‐pyrimidinyl) and‐1,3‐bis(2‐pyrazinyl)‐ derivatives of trans‐4,5‐dihydroxyimidazolidine (6). Details of the proposed mechanism are discussed.     

Access to β,γ-diamino acids. Application to the synthesis of 3-deoxyaminostatine

The synthesis of orthogonally protected diastereo- and enantiopure β,γ-diamino acids starting from natural α-amino acids is described, as well as its application to the synthesis of fully protected 3-deoxyaminostatine.     

Simple and convenient access to α,α,α-trisubstituted amides by double addition of Grignard reagents to acyl cyanohydrins

The double addition of Grignard (alkyl, aryl, alkenyl, alkynyl) reagents to acyl cyanohydrins was performed under unusually smooth conditions with a concomitant O-N acyl transfer, providing a very simple and general access to α,α,α-trisubstituted amides.     

Polyphosphoric Acid–Mediated,One-Pot,Novel Reactions to Build Polymethoxyarylnaphthalene Lignans

The one-pot reaction of succinic anhydride with 1,2-dimethoxybenzene furnished two structurally complicated polymethoxyarylnaphthalene lignans, polymethoxyarylnaphthol 1 as the minor product and polymethoxynaphtho[1,2-b]oxacycloheptatrienone 2 as the major product, in the presence of a small amount of polyphosphoric acid (PPA) as catalyst at 140°C and yielded 2 as a single product in good yield when a large amount of PPA as solvent was employed at 60–80°C. The novel structures of 1 and 2 were elucidated from ¹H NMR, ¹³C NMR, infrared (IR), and Electrospray ionization–mass spectrometry (ESI-MS) and further confirmed by x-ray diffractions. The possible mechanisms for the formation of 1 and 2 were also proposed.     

Apparent molar volumes of aqueous calcium chloride to 250°C, 400 bars,and from molalities of 0.242 to 6.150

Relative densities of CaCl ₂ (aq) with 0.22ml(mol-kg^–1)6.150 were measured with vibrating- tube densimeters between 25 and 250°C and near 70 and 400 bars. Apparent molar volumes V calculated from the measured density differences were represented with the Pitzer ioninteraction treatment, with appropriate expressions chosen for the temperature and pressure dependence of the virial coefficients of the model. It was found that the partial molar volume at infinite dilution V ^o , and the second and third virial coefficients B ^V and C ^V , were necessary to represent V near the estimated experimental uncertainty. The ionic-strength dependent ^(1)v term in the B ^V coefficient was included in the fit. The representation for V has been integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. The volumetric data indicate that the logarithm of the mean ionic activity coefficient, ln ±(CaCl ₂ ), increases by a maximum of 0.3 at 400 bars, 250°C, and 6 mol-kg^–1 as compared with its value at saturation pressure.     

X-rays to study,induce, and pattern structures in sol–gel materials

X-rays investigations have been shown to reveal important information regarding material features and the formation mechanism of mesostructured materials. Small angle X-ray scattering (SAXS) analysis performed using a synchrotron source has been very important in the optimization of the organization of mesoporous coatings obtained by evaporation induced self-assembly (EISA). The interaction between X-rays and ordered mesoporous films has only recently been reported, and new knowledge has been developed to use this external radiation source to tune the local material properties. Here we discuss the recent developments in X-ray lithography combined with sol–gel synthesis to pattern mesostructured and hierarchical porous coatings including the ability to tailor functionalized surfaces.