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The use of template-directed synthesis to obtain a new family of diastereoselective bowl-shaped molecules is demonstrated. They comprise a semirigid frame and adjustable size cavity capable of coordinating transition metal cations.

The total synthesis of racemic merrilactone A is described, which has featured a simultaneous and stereospecific creation of the C4 and C5 stereocenters via silyloxyfuran Nazarov cyclization. The results have suggested the participation of Lewis acidic silicon species in the Nazarov cyclization.

Stereoisomeric identification of norephedrine (NE) derived from methamphetamine (MA) or amphetamine (AM) was investigated by SIM-GC/MS assay using the urine of 33 MA abusers and 1 AM abuser. The assay simultaneously identified TFA-derivatized MA and AM metabolites, including AM, p-hydroxyl-MA (p-HMA), and p-hydroxyl-AM (p-HAM). The analysis lasted ~43 min, with a signal-to-noise ratio of [greater than or equal to] 3 and a detection limit of 50 ng/mL. Among 12 urine samples from different subjects, only the S (+) form of MA and its metabolites (AM, p-HMA, p-HAM) was detected, however, a (1R,2S)-(-)-NE stereoisomer was also identified. Among the urine samples of two subjects, only the R (-) form of MA and its metabolites (AM, p-HMA, p-HAM) was detected, while NE was not detected. Following urinalysis of urine obtained from 19 MA abusers and 1 AM abuser, only the (1R,2S)-(-)NE stereoisomer was identified, while unmetabolized MA, AM, and their metabolites (p-HMA, p-HAM), showed stereoselective metabolism. Although (1R,2S)-(-)-ephedrine (EP) alone was found in the urine of 1 (S)-(+)-MA user and 1 (S)-(+)- and (R)-(-)-MA user among 33 MA users, it was not present in the urine of the remaining 31 subjects. Therefore, (1R,2S)-(-)-NE was likely not of (1R,2S)-(-)-EP origin and was most likely from (S)-(+)AM of the MA metabolite. The production ratio of (1R,2S)(-)-NE to (S)-(+)-AM ranged from 0.01 to 0.25 in MA abusers and was 0.12 in AM abusers.

Based on the [Ni[(f-rac-L).sup.2+] and [[Ni[(CN).sub.4]].sup.2-] building blocks (L=5,5,7,12,12,14-hexamehtyl -1,4,8,11-tetraazacyclotetradecane), three helical supramolecular stereoisomers of meso-2, [DELTA]-2 and [DELTA]-3 were constructed. Complete examination of the structure indicates that the interchain hydrogen bonding and hydrophobic interactions play an important role in the transfer of chirality between neighboring helical chains due to which one dimensional (1D) helical chains are packed in an achiral or homochiral manner.

Studies conducted on the molecular modeling and molecular dynamics (MD) simulations of the 4-hydroxyequilenin (4-OHEN)-A adducts in DNA 11-mer duplexes are presented. Similar stereochemical principles govern the orientations in DNA duplexes of the 4-OHEN-A adducts as for the analogous C adducts, with opposite orientations of the equilenin rings in stereoisomeric pairs of adducts characterized by near-mirror image circular dichroism (CD) spectra.

Techniques of fluorous mixture synthesis are used to make four candidate stereoisomers for the natural product lagunapyrone B. Stille coupling of the resulting pure quasienantiomers with the quasiracemic mixture has provided two quasi-diastereomeric samples that are demixed and detagged to provide all four lagunapyrone B stereoisomers, which are assigned the 6R,7S,19S,20S,21R configuration by comparison of optical rotations.

A multigram scale synthesis of the four stereoisomers of methyl 3-silylglycidates (epoxysilanes) with high enantiopurity is developed. These epoxysilanes possess utility as chiral building blocks in organic synthesis and a Sharpless asymmetric epoxidation and an enzymatic resolution are employed to obtain the enantiomerically enriched epoxysilyl alcohols, thus providing access to all four stereoisomers in both the cis/trans series.

The principles of the oligoethylene glycol (OEG) mixture synthesis are described with the synthesis of all four possible stereoisomers of a hydroxybutenolide fragment common to murisolin and many other acetogenins. The reaction, analysis, separation and characterization of OEG mixture synthesis are described and compared to and contrasted with those of flourous mixture synthesis.

The stereoselective constructions of the three key building blocks required for the total synthesis of the originally proposed structure of azaspiracid-1 are described. Additionally, a description is presented of the synthetic technologies that could potentially be used to assemble the entire skeleton of the structure of azaspiracid-1, including a method for connecting all fragments and casting ring G.

The crystal and molecular structures of two new phosphorochromones was studied to obtain information about their stable tautomers. The results indicated that the systems with N-H...O intramolecular hydrogen bonds are more stable than those containing O-H...N bonds.

A stereoselective synthesis of (S)-(+)-cocaine, the unnatural enantiomer is reported. The method used can provide access to enantiomerically pure analogues of cocaine and other medicinally significant tropane alkaloids and also be useful in asymmetric synthesis.

Substrate-controlled 1,5-syn and -anti stereoinduction in the aldol reaction of [beta]-tris(trialkylsilyl)siloxy methyl ketones is achieved with high diastereoselectivities. Tris(trialkylsilyl)silyl groups are prepared, which have played a vital role in the selectivities of these reactions and the 1,3,5-triol stereoisomers are prepared from [beta]-siloxy methyl ketones.

A concise enantioselective total synthesis of (2S,3R,4S)-4-hydroxyisoleucine and its stereoisomers is described. A key feature of the method is a catalytic enantioselective mannich reaction that is either anti- or syn-selective as genesis of chirality.

The application of the ring-size-selective enyne metathesis approach for the desymmetrization of an enantiopure [C.sub.2]-symmetric building block is discussed. The presence of an unprotected hydroxy group is shown to act as the major factor that controls the ring-size selectivity in the reaction.

The 11-12 step total syntheses of all stereoisomers of phenatic acid B and determination of their absolute configuration are described. The synthetic processes are based on an efficient combination of the Sharpless asymmetric dihydroxylation, the Johnson-Claisen rearrangement, and hydroboration-oxidation.

The synthesis and characterization of the first potent inhibitor of Neisseria meningitidis sialic acid synthase (NeuB) is described. The inhibitor is a stable deoxy analogue of the tetrahedral intermediate that forms in the NeuB reaction and is prepared as a mixture of stereoisomers at the key tetrahedral center.

Thermodynamic stereocontrol of the (hexamethyldisilazide)magnesium enolates of propiophenone in THF is described. Interconversion among aggregates is very slow, whereas stereoisomerization of the monomer, even in the absence of a proton source such as ketone or amine, is very fast and it has taken place in the absence of a proton source or excess ketone.

A 'shortcut' of the advanced Mosher rule is proposed for using in assigning stereocenters in molecules with elements of local symmetry. The Mosher esters are used for assigning the (3S,14S) configuration to petrocortyne A and for validating both the standard and shortcut Mosher methods for using in the petrocortyne family of dialkynyl carbinols.

A short, convenient, gram scale protocol is established for allowing the facile access to all four stereoisomers of 2-aminocyclobutanecarboxylic acid, each in enantiomerically pure form. Cis-racemate is used as the starting material and the method has combined [alpha]-phenylethylamine derivative resolution and controlled cis-to-trans epimerization procedures.

A bulky group of guest substrate located outside the host cavity has manipulated the stereoselectivity of photoreaction occurring inside the cavity. This has helped in achieving a dramatic inversion of the head-to-tail/head-to-head (HT/HH) ratio by just switching the host from [gamma]-cyclodextrin ([gamma]-CD) to cucurbit[8]uril (CB[8]) in the photodimerization.

The relative configuration of acyclic [alpha]-alkyl-[beta]-hydroxy carbonyl compounds is determined using [super 1]H NMR spectroscopy. A simple method is proposed for assigning the relative configuration of the compounds.

The reaction of [([super i][P.sub.2]PE).sub.2]NM.TMEDA (M = Li, E = Se, M = Na, E = Ta) with Ni[Br.sub.2].DME in THF has produced Ni[[[(SeP[super i][P.sub.2]).sub.2]N].sub.2] as either square-planar or tetrahedral stereoisomers, depending on the recrystallization solvent. The Te analogue can be obtained as the square-planar complex Ni[[[(TeP[super i][P.sub.2]).sub.2]N].sub.2].

The total syntheses of five palmerolide A stereoisomers and the revised [ent-(19-epi-20-epi-1) structures are described. The Homer-Wadsworth-Emmons olefination and the Yamaguchi lactonization are examined and are successful as a means to construct the palmerolide macrocycle.

The dynamic behavior of three-dimensional structures of the two conformers formed by pyoverdine PvdI, a peptidic siderophore from Pseudomonas aeruginosa with metal ions Ga(III) is demonstrated. The structural analysis indicates that the observed conformational exchange involves a stereoisomerization of the metal binding coordination accompanied by a change in the global shape of the siderophore.

The studies about a set of stereoisomer which have optically active as well as optically inactive component are described. One example of such racemic compound is tartaric acid which contains both optically active and optically inactive members.

An efficient method is described for preparing the four stereoisomers of 6-amino-3-azabicyclo[3.2.1]octane-6-carboxylates by using (R)-1-phenylethylamine as the chiral-inducing moiety. A series of N-3-alkyl compounds are prepared by using a one-pot deprotection-alkylation method starting from these compounds.

New chiral fluorinated amino and azamacrolactones of two types are synthesized by using a ring-closing metathesis (RCM) reaction. The method allows the preparation of the desired fluorinated macrolactones in excellent yields.

The synthesis of hodgkinsine stereoisomers appended with a third cis-pyrrolidinoindoline ring to a hexacyclic chimonanthine precursor is presented.

Synthesis of sn-(3-myristoyl-2-hydroxy)glycerol-1-phospho-sn-1'-(3'-myristoyl-2'-hydroxy)glycerol (1,1'-DMBMP) is presented. X-ray measurements revealed that these DMVMPs undergo an unbinding at the main phase transition temperature.

The total syntheses of two 16-member libraries of murisolins are reported by which the fluorous mixtures are subjected to hydrogenation, double demixing and detagging to provide the isomerically pure murisolins. The synthesis reveals that a combination of solution phase mixture synthesis techniques with synthetic plans using minimum steps results in a substantially improved number of synthetic stereoisomers of complex compounds.

The synthesis of 2-C-trifluoromethylerythritol from 1,1,1-trifluoro-2,3-epoxypropane is described. The four stereoisomers are achieved in good yields by an improved asymmetric dihydroxidation with moderate to high ee.

An experiment illustrating stereochemical principles, like different physical properties in achiral environments, assignment of absolute stereochemistry, and the stereoisomeric relationships to differences in absolute stereochemistry is devised. A demonstration of how enantiomers have the same physical properties until placed in chiral environments using Menthol stereoisomers is described.

The experiment involving enantiomeric resolution, as an illustration of chiral technology, is an excellent early organic chemistry lab experiment. The success of this enantiomeric resolution can be judged by melting point, demonstrated by (plus or minus)-mandelic acid- (1R, 2S)-(-)-ephedrine system.

A stereoselective synthesis of four stereoisomers of beta-methoxytyrosine from (S)- and (R)-serine is accomplished. Both threo and erythro diastereomers of (2S)- and (2R)-beta-methoxytyrosine can be selectively synthesized from (S)- and (R)-serine, respectively.

Total syntheses of the morpholine-2,5-dione, Bassiatin, and its stereoisomers, is completed with a key step in the syntheses, the Mitsunobu cyclization of hydroxyacid acyclic precursors. The hydroxyacid precursors are hindered alcohols and two substrates underwent Mitsunobu cyclization with retention of configuration, whereas the other two substrates underwent Mitsunobu cyclization with either retention or inversion of configuration depending on reaction conditions.

The first synthesis of all four stereoisomers of 1,3,5,7-tetrahydroxyl-1,3,5,7-tetraisopropylcyclotetrasiloxane, [i-PrSiO(OH)](sub 4) is presented. A combination of dephenylchlorination of tetraarylcyclotetrasiloxanes and the following hydrolysis proved to be an efficient method for the stereospecific transformation of aryl-substituted cyclotetrasiloxanes into (i-PrSiO(OH))4.

Optically active aziridine derivatives have attracted considerable attention because of their versatile synthetic utilities, and a variety of methods for asymmetric syntheses are reported. Methods for the regio-and stereoselective ring cleavage of the aziridines are well studied, and are still under active investigation for the syntheses of chiral amines, amino alcohols, and amino acids.

The enzyme-mediated preparation and the odor evaluation of the single stereoisomers of the commercial odorants Muguesia and Pamplefleur are described. The synthetic approach to Muguesia stereoisomers helped to clear the assignment of the relative configuration of intermediate diols.

A synthetic study to extend the aromatic cavity of the CTV platform is conducted using its phenol groups for anchoring three aromatic moieties and the other three oxygen atoms to increase the lipophilicity of the receptor. Attempts to perform alkylation reactions on derivatives evidenced the formation of a stereoisomeric mixture of symmetrical and unsymmetrical compounds.

A Nazarov cyclization/Wagner-Meerwein rearrangement pathway that produces unusual spirocyclic products is described. The transformations are found to be highly stereoselective, efficient for a range of substrate types and are capable of creating adjacent quaternary centers.

Studies were conducted to investigate the switch from oxygen to carbon functionality featuring a Wittig rearrangement as the key step. High crystallinity and a narrow melting range suggested that a single diastereoisomer was formed in the course of the Wittig rearrangement, and this was confirmed by the X-ray crystallography of the 4-bromobenzoate.