Ray Crystallographic Analysis and

X-Ray Crystallographic Analysis and Structure-Based Drug Design. 32... 

Silanethione 38 was characterized by H, 13C, and 29Si NMR, Raman, and UV-vis spectroscopic methods. The 29Si NMR chemical shift of 38 (8Si 166.56/C6D6) for the silathiocarbonyl unit is much downfield shifted from those of the thermodynamically stabilized silanethiones, 31, 34, 35,28 and 36,29 mentioned in the previous sections, clearly indicating a genuine Si=S double bond in 38 without any intra- or intermolecular coordination. The molecular structure of 38 was successfully established by X-ray crystallographic analysis, and the detailed structural parameters are discussed in the following section. 

Swainsonine is a trihydroxylated bicyclic indolizidine alkaloid with four chiral centres, whose relative stereochemistry was determined by X-ray crystallographic analysis and the absolute configuration was deduced on the basis of biosynthetic and asymmetric induction studies, and then confirmed by an enantiospecific synthesis from D-mannose [2a]. 

It is interesting to note that the yield of 39 can be increased to 95 % in the presence of a Ni(0) catalyst (see Section I.3.I.2.).43 In unsymmetrically substituted buta-l,2,3-trienes, head-to-head dimerization takes place as well, as seen in the examples below.44 The intermediate cyclopropy-lidenecumulenes 41 are formed from vinylidene insertions into alkenes and reactions occur at the terminal unsaturated site of the cyclopropylidene group. Structures 42 were confirmed by X-ray crystallographic analysis and revised the original assignment of the head-to-tail structures for these derivatives.45... 

Isolation and Structure Proof. The maytansinoids were (lie first ansamacrolides to be found in plants. The term maytansinoids refers to those ansamacrolides related to maytansinc, whereas the term maytansides refers to maytansinoids lacking the ester side chain at C-3 as well as the corresponding elimination products. Maytansine was first isolated from the alcoholic extract of Maytenus ovatus Loes. Several other maytansinoids and maytansides have been isolated from this species. The structure of niaytan-sine was established by x-ray crystallographic analysis, and the structures of the other maytansinoids and maytansides were arrived at by comparative nmr studies using maytansine. The absolute configuration of maytansine is 3(5), 4(5), 5(5), 6(R), 7(5), 10(5), and 2 (5). 

Sonnet, Flippen, and Gilardi89 prepared the iminium salt 35 from 4-bromopyrrole-2-aldehyde with DM AD it gave a 1 1 molar adduct (36) (38%) whose structure was determined by an X-ray crystallographic analysis, and a 1 2 adduct (37) (43%). 

The single-crystal to single-crystal nature and the steric course of the photodimerization of thiocoumarin (102) to (+)-a t/-head-to-head dimer (103) in the inclusion complex were investigated by x-ray crystallographic analysis and x-ray powder diffraction spectroscopy [54],... 

W.G., Marathe, P., Bursuker, I., Kellar, K.A., Roongta, U., Batorsky, R., Mul-heron, J.G., Bol, D., Fairchild, C. R., Lee, F. Y., Webster, K. R. Discovery of amino-thiazole inhibitors of cyclin-dependent kinase 2 synthesis, X-ray crystallographic analysis and biological activities. Journal of Medicinal Chemistry 2002, 45, 3905-3927. 

Table 2.1 Experimental data from X-ray crystallographic analysis and theoretical optimized structures of model compounds A and B...

An account has appeared on the preparation, structure and reactivity of a series of metallaphosphoranes. For example, the transition metal complex (2) reacts with (3ab) to form (4ab). X-ray crystallographic analysis and spectroscopic data for these metallaphosphoranes reveal that the transition metal fragment serves as a strong n donor towards the phosphorane fragment. The account also reports the activation parameters for pseudorotation about phosphorus in several metallaphosphoranes with values ranging from 67.8 to 89.7 kJmoP dependent upon the metal centre (Co, Ru or Fe) and the substituents in the Cp ring. 

Computational chemistry applied to drug design relies on two major experimental sources of detailed three-dimensional (3-D) data 1) X-ray crystallographic analysis and 2) nuclear magnetic resonance (NMR) spectroscopy. 

It is evident that the three new aromatics (208—210) isolated from the New Zealand liverwort Balantiopsis rosea stem from a bibenzyl. The structure of compound 209 was established by NMR and X-ray crystallographic analysis and the absolute configurations of these structures were determined by CD analysis [104]. 

Thus, both X-ray crystallographic analysis and NMR linewidth study support the interpretation that in compounds 89-92 incipient dative bonding between oxygen (or sulphur) and germanium takes place though it may be weaker than that between nitrogen and germanium in the similar structure 93. 

Since the previously published review (8), novel 4-aryltetrahydroiso-quinoline type alkaloids have not been found in the Amaryllidaceae plants. Only latifine (437) has been isolated from the bulbs of Crinum latifolium (200). The structure was confirmed by spectroscopic evidence. X-ray crystallographic analysis, and synthesis (198). 

This methodology was employed for the synthesis of the reported structure of the alkaloid jamtine (02OL715, 02JOC929). The key sulfoxide intermediate 307 was heated with CSA to produce several tricyclic products (98% yield) as a mixture (5 2 1 1) of diastereomers in which 308 predominated (Scheme 57). The stereochemistry of 308 was secured by X-ray crystallographic analysis and is consistent with a Nazarov-type conrotatory 47i-electrocyclization followed by attack of the nucleophilically disposed aromatic ring from the least hindered side of the intermediate iminium ion. Reaction of a-ethylthio amide 308 with NaH effected an intramolecular alkylation to provide tetracycle 309. 

Evidence for the /3-d configuration of the anomeric center (C-1) of the purine nucleosides derived from the nucleic acids was obtained by Fur-berg, using x-ray crystallographic analysis, and by Todd and coworkers, whose studies of the anhydronucleosides (7 and 8) derived from... 

The structures of a number of 292 and 293 have been studied by X-ray crystallographic analysis and semiempirical molecular orbital calculation (AMI) and ab initio (HF/3-2IG) methods (99T875, 06MI599, 05AX(E)04372, 05AX(E)03536) (Scheme 54). 

This selectivity can be understood by assessing the possible conformations of the oxolactone using a combination of X-ray crystallographic analysis and molecular mechanics calculations, then making suitable assumptions about the reactivity and stereochemical preferences of the various species. This approach is still hindered by the complexity of the calculations involved, particularly if a full survey of the conformational space of the substrate is to be attempted. 

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