The structure and properties of hybrid fluorous-hydrocarbon fatty acids

A series of long chain fatty acids is prepared with alternating blocks of fluorocarbon and hydrocarbon. This hybrid construction provides three domains (fluorous, hydrocarbon, hydrophilic) on the same molecule. The ability of the monocarboxylic acids to form monolayers on water is explored and, in selected cases, X-ray structure analysis of the dicarboxylic acids provides information on the conformation and solid state organisation of these molecules. The hybrid molecules display surface behaviour and show packing distances which are intermediate between alkyl and perfluoroalkyl chains.     

Studies toward the synthesis of luminacin D: assembly of simplified analogues devoid of the epoxide displaying antiangiogenic activity

[reaction: see text] A series of structurally simplified luminacin analogues devoid of the epoxide ring are assembled in a stereocontrolled manner from 2,4-dimethoxybenzaldehyde using a syn-selective aldol reaction as the key step. The success of the approach is critically dependent on the nature and extent of the alcohol protecting groups. The synthetic analogues inhibit VEGF-stimulated angiogenesis in an in vitro assay indicating that the epoxide is not essential for biological activity in this compound class.     

Half-rotation in a [2]catenane via interconvertible Pd(II) coordination modes

Reaction of a [2]catenane with Pd(OAc)2 binds both macrocycles to the metal, locking them in position; treatment with PdCl2, however, results in coordination of only one ring, producing a half-turn in the relative orientation of the [2]catenane components in both solution and the solid state.     

Synthetic studies related to diketopyrrolopyrrole (DPP) pigments. Part 3: Syntheses of tri- and tetra-aryl DPPs

Novel synthetic methodologies leading towards 2,3,5-triaryl- and 2,3,5,6-tetraaryl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-diones (tri- and tetra-aryl-DPPs) and their derivatives have been investigated. Direct arylation of 3,6-diphenyl-DPP was possible using 1-fluoro-2,4-dinitrobenzene. Acylation of ethyl 2-aryl-4,5-dihydro-5-oxopyrrole-3-carboxylates with N-arylbenzimidoyl chlorides in the presence of a strong base gives the novel 2,3,6-triaryl-DPPs together with the corresponding uncyclised enamines. A new and simple method for the synthesis of ethyl 1,2-diaryl-4,5-dihydro-5-oxopyrrole-3-carboxylates has led to an alternative route to triaryl-DPPs via reaction with benzonitrile under basic conditions, and combination of this with the benzimidoyl chloride methodology has enabled the synthesis of variously substituted 2,3,5,6-tetraphenyl-DPPs.     

Tandem sequential catalytic enantioselective synthesis of highly-functionalised tetrahydroindolizine derivatives

An isothiourea-catalysed enantioselective synthesis of novel tetrahydroindolizine derivatives is reported through a one-pot tandem sequential process. The application of 2-(pyrrol-1-yl)acetic acid in combination with either a trifluoromethyl enone or an α-keto-β,γ-unsaturated ester in an enantioselective Michael addition–lactonisation process, followed by in situ ring-opening and cyclisation, led to a range of 24 tetrahydroindolizine derivatives containing three stereocentres in up to >95 : 5 dr and >99 : 1 er.

The isothiourea-catalysed enantioselective synthesis of tetrahydroindolizine derivatives containing three stereocentres is reported through a one-pot tandem sequential process.     

Preparation and coordination chemistry of N-diallylaminodiphenylphosphine and N-allylaminobis(diphenyl)phosphine

N-diallylaminodiphenylphosphine and N-allylaminobis(diphenyl)phosphine have been prepared by reaction of the appropriate amine with Ph₂PCl. The coordination chemistry of these phosphines has been studied with a range of metals [Pd, Pt, Rh, Ir, Au, Ru, Mo]. Whilst the majority of the complexes are simple bidentate P,P donors, in the case of N-diallylaminodiphenylphosphinecoordination can involve the CC group or the nitrogen centre.     

Switching "on" and "off" the expression of chirality in peptide rotaxanes

The hydrogen-bond-directed synthesis, X-ray crystal structures, and optical properties of the first chiral peptide rotaxanes are reported. Collectively these systems provide the first examples of single molecular species where the expression of chirality in the form of a circular dichroism (CD) response can selectively be switched "on" or "off", and its magnitude altered, through controlling the interactions between mechanically interlocked submolecular components. The switching is achievable both thermally and through changes in the nature of the environment. Peptido[2]rotaxanes consisting of an intrinsically achiral benzylic amide macrocycle locked onto various chiral dipeptide (Gly-L-Ala, Gly-L-Leu, Gly-L-Met, Gly-L-Phe, and Gly-L-Pro) threads exhibit strong (10-20k deg cm(2) dmol(-1)) negative induced CD (theta;) values in nonpolar solvents (e.g. CHCl(3)), where the intramolecular hydrogen bonding between thread and macrocycle is maximized. In polar solvents (e.g., MeOH), where the intercomponent hydrogen bonding is weakened, or switched off completely, the elliptical polarization falls close to zero in some cases and can even be switched to large positive values in others. Importantly, the mechanism of generating the switchable CD response in the chiral peptide rotaxanes is also determined: a combination of semiempirical calculations and geometrical modeling using the continuous chirality measure (CCM) shows that the chirality is transmitted from the amino acid asymmetric center on the thread via the macrocycle to the C-terminal stopper of the rotaxane. This understanding could have important implications for other areas where chiral transmission from one chemical entity to another underpins a physical or chemical response, such as the seeding of supertwisted nematic liquid crystalline phases or asymmetric synthesis.     

Platinum complexes of naphthalene-1,8-dichalcogen and related polyaromatic hydrocarbon ligands

Platinum bisphosphine complexes bearing dichalcogen-derivatised naphthalene, acenaphthene or phenanthrene ligands have been prepared by either oxidative addition to zero-valent platinum species or from [PtCl(2)(PPhR(2))] (R=Ph or Me) and the disodium or dilithium salts of the parent disulfur, diselenide or mixed S/Se species. The parent naphthalene, acenaphthene and phenanthrene chalcogen compounds were treated with either [Pt(PPh(3))(4)] or [Pt(C(2)H(4))(PMe(3))(2)] (prepared in situ from [PtCl(2)(PMe(3))(2)], ethene and sodium naphthalide or super hydride [LiBEt(3)H]) to give the appropriate platinum(II) species. The dilithium salts of 1,8-E(2)-naphthalene (E=S or Se) prepared in situ by reduction of the E-E bond with [LiBEt(3)H] were treated with [PtCl(2)(PPh(3))(2)] to give [Pt(1,8-E(2)-nap)(PPh(3))(2)]. The tetraoxides [Pt(1,8-(S(O)(2))(2)-nap)(PR(3))(2)] (PR(3)=PPh(3) or PMe(2)Ph) were prepared in a similar metathetical manner from the appropriate [PtCl(2)(PR(3))] complexes and the disodium salt of naphthalene 1,8-disulfinic acid (1,8-(S(O)ONa)(2)-nap). The X-ray structures of selected examples reveal bidentate coordination with the naphthalene-E(2) unit hinged (111-137 degrees) with respect to the coordination plane. The naphthalene ring suffers significant distortion from planarity.