Nonproteinogenic a,a-disubstituted-a-amino acids have attracted considerable attention because of their utility as conformational modifiers of biologically active peptides and as enzyme inhibitors. Typical methods for asymmetric synthesis of them involve chiral auxiliary-based enolate chemistry (ref. 1). However, the most straightforward strategy for the synthesis would involve direct asymmetric a-alkylation of parent a-amino acids in the absence of additional chiral sources such as chiral auxiliaries, chiral ligands, or even chiral catalysts. Since both L- and D-a-amino acids are readily commercially available, the synthetic route shown in Scheme 1 seems most attractive for the purpose. However, this process usually gives racemic a-alkylated products from either L- or D-a-amino acid because the enolate formation eliminates the chiral information of C(2) and an achiral enolate common to both L- and D-series is formed (A = B). If enolate intermediates enable to memorize the chiral information at C(2) of the starting materials, L- and D-a-amino acids would give optically active L- and D- (or D- and L-) a,a-disubsituted a-amino acids via intrinsically chiral enolate intermediates A and B, respectively. In this paper, we describe asymmetric a-alkylation of a-amino acid derivatives via the synthetic route

Attachment of a chiral imidazole or chiral oxazoline to either (h5-cyclopentadienyl)(h4-tetraphenylcyclobutadiene)cobalt or pentaphenylferrocene results in the heterocycle mimicking an environment of planar chirality. This chiral relay effect is demonstrated by both highly diastereoselective palladation and application of the oxazoline complexes as ligands in asymmetric catalysis.

Studies of chiral Lewis acid catalyzed enantioselective reactions using strongly coordinating nucleophiles, as a rather unexplored categoly of catalyzed enantioselective reactions, are described. Selection of a proper chiral catalyst should be essential. The author has employed complexes of two chiral ligands, (R,R)-4,6-dibenzofurandiyl-2,2'-bis(4-phenyloxazoline) and (R,R)-isopropylidene-2,2'-bis[4-(o-hydroxybenzyl)oxazoline)], designated R,RDBFOX/Ph and R,R-BOX/o-HOBn, respectively. The complex catalyst derived from R,R-DBFOX/Ph and Ni(ClO4)2 . 3H2O works as a powerful catalyst in the enantioselective thiol conjugate additions to 3-(2-alkenoyl)-2-oxazolines, and the complex derived from R,R-BOX/o-HOBn and Cu(OTf)2 catalyzes the reactions of O-benzylhydroxylamine to 1-alkyl-3-(2-alkenoyl)-2-imidazolidinones. Internal delivery of nucleophiles to the activated acceptors is proposed as a powerful principle for the development of the titled reactions

The cyclic hydroboration of 2,7-dimethyl-2,6-octadiene was studied. It was found that the stereochemical outcome of the reaction was dependent upon the solvent, temperature, time, and the nature of the borane reagent. Monobromoborane in carbon tetrachloride at 76 oC gave after 8 hr a 4:1 mixture of trans:cis-2,5-diisopropylborolane. Pure racemic trans-2,5-diisopropyl borolane was isolated following selective complexation of the cis-2,5-diisopropylborolane with 1-(2-hydroxyethyl)-pyrrolidine.

Oxidation reactions are at the core of asymmetric chemistry. It is therefore surprising, in view of the potential applications, not to find any instances of the notion of using a "chiral cation" to distinguish between a pair of prochiral hydrides during hydride transfer [H-T]. To the best of our knowledge, there are none. Yet, the converse concept of using a "chiral anion" to distinguish between a pair of prochiral protons during a deprotonation has led to significant advancements in the field of asymmetric synthesis.[1] This letter describes the first example of an enantioselective [HT]

One of most interesting objects for studying the ability of polyfunctional nucleophiles is the nitromethyl derivatives series of 1,2,3,4-tetrazole, which also have wide practical application. Some derivatives in that series can be used for the synthesis of medicinal preparations, however in the literature there is no information on the synthesis of mononitrometyltetrazoles with nitromethyl’s group in position 2. The aim of this work was to synthesize 2-nitromethyl-5-nitro-1,2,3,4-tetrazole (NMNT) and to investigate its structure.

ß-Amino acids and their peptides have most recently found intense interest in the research community [1].Oligomers ("foldamers") of unnatural amino acids have a wide range of potential applications. They may adopt compact, specific conformations. They could be used to form helices, turns and sheets and develop new types of tertiary structures. Certainly short peptides of this type have potential pharmaceutical applications.

Dendrimer is a compound word, composed of the Greek "dendron", meaning tree and the word "polymer", that itself is a fusion of the Greek "poly" (many) and "meros" (part). Dendrimers can be divided in three zones: The region of the initiator core, the region of the inner branching units and the outer level, carrying the endgroups. Figure 1 shows the building of a two dimensional Dendrimer. The chemistry of the Dendrimers is a modern and new working field, that brought out a lot of interesting and aesthetic molecules. In future the synthesis of further interesting structures can be expected. The first work [1] initiated a great, almost exponentially, growing number of publications [2]. This new field of research is of academic interest and the industrial research hopes of new positive properties belonging to this new class of molecules, too

Alternative synthetic routes to androst-4-ene-1a,17b-diol-3-one (1a-hydroxytestosterone) have been investigated. Within this objective numerous reported reductions have been reviewed and synthetically evaluated

Polymer-supported electrophilic halogenate(I) complexes 2 and 3 promote smooth addition to vinyl and allylsilanes without loss of the silyl group. In conjunction with Amberlyst A26 (OHs -form) vinyl silanes are converted into epoxysilanes in one pot.