A sterically congested 1,2-diphosphino-1'-boryl-ferrocene: synthesis, characterization and coordination to platinum.

A new class of tritopic ferrocene-based ambiphilic compounds has been prepared by assembling diphosphino- and boryl-substituted cyclopentadienides at iron. The presence of five sterically demanding substituents on the ferrocene platform induces conformational constraints, as is apparent from XRD and NMR data, but does not prevent the chelating coordination to platinum. The Lewis acid moiety is pendant in both the free ligand and the platinum complex.

A general diastereoselective synthesis of highly functionalized ferrocenyl ambiphiles enabled on a large scale by electrochemical purification.

A general synthesis of highly functionalized ferrocenes, which include (P,B)- and (N,B)-ambiphiles, has been developed at a multigram scale. Diastereoselective stepwise modification of di-tert-butylated ferrocenes included the unprecedented separation of electroactive species. Bulky alkyl groups on ferrocenes ensure planar chirality of ambiphiles and enforce closer proximity of antagonist Lewis functions.

Planar-Chiral 1,1'-Diboryl Metallocenes: Diastereoselective Synthesis from Boryl Cyclopentadienides and Spin Density Analysis of a Diborylcobaltocene.

The reaction of nonsubstituted alkali metal cyclopentadienides with haloboranes leads to ∼90:10 mixtures of isomeric diene products that can be deprotonated to give simple boryl cyclopentadienides. We extended this transformation to the sterically hindered lithium tert-butylcyclopentadienide 1 using FBMes (Mes = 2,4,6-trimethylphenyl) and ClBCy as electrophiles. The boryl group is selectively introduced in the remote position to minimize steric congestion.

Synthesis and structure of symmetrical bicyclic hexapeptides bridged by metathesis reaction.

[structure: see text] Bicyclic hexapeptides 1a-c were synthesized via an intramolecular ring-closing metathesis reaction on solid phase followed by an N- to C-terminal cyclization in solution. Structural elucidation showed that these compounds assumed a C2-symmetrical structure with two beta-turns. The trans-ethylene plane was found to occupy two positions in rapid interconversion.

Structure activity relationships of new inhibitors of mammalian 2,3-oxidosqualene cyclase designed from isoquinoline derivatives.

We have designed more potent inhibitors from the previously reported LF 05-0038, a 6-isoquinolinol based inhibitor of 2,3-oxidosqualene cyclase (IC50: 1.1 microM). Replacement of the 3-OH group by various 3-substituted amino groups, and modification of the alkyl chain borne by the endocyclic nitrogen led to inhibitors with IC50 in the range of 0.