Ketones crystal structures

Fig. 7.3. Crystal structures of some lithium etiolates of ketones. (A) Unsolvated hexameric enolate of methyl t-butyl ketone (B) tetrahydrofuran solvate of tetramer of enolate of methyl r-butyl ketone (C) tetrahydrofuran solvate of tetramer of enolate of cyclopentanone (D) dimeric enolate of 3,3-dimethyl-4-(r-butyldimethylsiloxy)-2-pentanone. (Structural diagrams are reproduced from Refs. 66-69.) by permission of the American Chemical Society and Verlag Helvetica Chimica Acta AG.

While wild-type PAMO was unable to convert 2-phenylcyclohexanone efficiently, all deletion mutants readily accepted this ketone as substrate. All mutants also displayed a similar thermostability when compared with the parent enzyme. The most active mutant (deletion of S441 and A442) was used for examining its enantioselective properties. It was found that the mutant preferably formed the (/ )-enantiomer of the corresponding lactone E = 100). While CHMO also shows a similar enantioselective behavior, this PAMO deletion mutant is a better candidate for future applications due to its superior stability. This clearly demonstrates that PAMO can be used as parent enzyme to design thermostable BVMO variants. It also illustrates that the available crystal structure of PAMO will be of great help for BVMO redesign efforts. ... 

Fig. 1.1. Crystal structure of lithium enolate of methyl -butyl ketone in a structure containing four Li+, two enolates, and one HMDA anions, one bromide ion, and two TMEDA ligands. Reproduced from Angew. Chem. Int. Ed. Engl., 35, 1322 (1996), by permission of Wiley-VCH.

Fig. 1.6. Crystal structure of dimer of lithium salt of N-phenylimine of methyl -butyl ketone. Two molecules of diethyl ether are present. Reproduced from J. Am. Chem. Soc., 108, 2462 (1986), by permission of the American Chemical Society. 

Spectroscopic investigations of the lithium derivatives of cyclohexanone (V-phenylimine indicate that it exists as a dimer in toluene and that as a better donor solvent, THF, is added, equilibrium with a monomeric structure is established. The monomer is favored at high THF concentrations.110 A crystal structure determination was done on the lithiated A-phenylimine of methyl r-butyl ketone, and it was found to be a dimeric structure with the lithium cation positioned above the nitrogen and closer to the phenyl ring than to the (3-carbon of the imine anion.111 The structure, which indicates substantial ionic character, is shown in Figure 1.6. 

The crystal structure of (232) is reported. Ir complexes bound to the multidentate ligand as in (232) have proved successful in the enantioselective reduction of a,/3-unsaturated ketones to allylic alcohols.404... 

The late stages of the synthesis (Scheme 1.17) proceeded with Wittig methylenation of ketone 144 with Ph3P=CH2 at 70 °C to furnish exocyclic alkene 145 in 77 % yield. Finally, the alcohol was installed via a Se02-mediated allylic hydroxylation [57] of the exocyclic alkene 145 to afford ( )-nominine (1) in 66 % and 7 1 dr. The structure of nominine (1) was verified via an X-ray crystal structure determination, thereby completing the racemic total synthesis of ( )-nominine (1). 

In an early attempt to correlate reactivity and structure Guy et al. (1977) compared the crystal structure of the steroidal ketone [56] with those of related compounds. The regioselectivity and rapid rate of the base-catalysed... 

We have already described some proton-transfer processes that occur without disruption of the crystal structure. We now treat two other homogeneous reactions. The first of these is the (2 + 2) photocyclodimerization of a number of benzylidene ketones (185,186). These monomers are based on one of the three frameworks 124 to 126. The three parent molecules and a number of their... 

The chloromethyl ketone-based inhibitor-complex crystal structures suggested the strand E993-P996 as a recognition strand for the unprimed-substrate residues. 

Based on these findings, new pentacoordinated Ir complexes [lr(cod) (S)-(+)-(NNR )1] were synthesized and characterized also by X-ray crystal structure determination by the same authors (NNR = 2-pyridinal-l-phenyhethylimine, PPEI, 77a 2-acetylpyridine-l-phenylethylimine, APPEl, 77b Scheme 4.32). The complexes were tested in the ATH of ketones in isopropanol and the data compared with results obtained using the corresponding square planar complexes [Ir(cod) (R) -(-)PPE1 ]C104 (76d) [67]. 

Crystalline packing is an important parameter for auto-oxidation in the sohd state, as molecular oxygen must be able to access susceptible moieties in the molecule. Lyn et al. [63] showed that only one (hexagonal form) of the five different polymorphic forms of prednisolone tert-butylacetate were susceptible to oxidation, yielding the 11-ketone product. The authors attributed this oxidative reactivity to channels in the crystal structure allowing access to the labile 11-alcohol position. Bryn et al. [64] also identified a similar phenomenon in the photo-mediated oxidation of 21-cortisol tert-butylacetate to the corresponding ketone. 

Ketonate complexes of Ru are reported in a number of papers. The parent complex [Ru(acac)3] has been subject to a polarized neutron diffraction study at 4.18 K, to powder neutron diffraction studies and to single-crystal structure determinations at 293 K, 92 K, and 10.5 K. The structure is disordered at all temperatures. Measurements of the magnetic susceptibilities (at 2.5 K and 300 K) have been made along different crystal axis directions, and the results analyzed. An investigation of the relationships between ionization potentials and half-wave potentials of a series of tris(/3-ketonate)Ru complexes has been reported, and the electrochemical properties of [Ru(acac)3] in chloroaluminate molten salt media have been reported. The reduced species [Ru(acac)3] can react with AICI4 reduction by bulk electrolysis of a small amount of [Ru-(acac)3] in the melt yields [RuClg]. ... 

Figure 17.3 Schematic representation of the design of the symmetric cathepsin K inhibitor diacylaminomethyl ketone (1,3-bis[[A/-[(phenylmethoxy)carbonyl]-L-leucyl]amino]-2-propanone), based on the crystal structures of papain bound to leupeptin (Leu-Leu-Arg-aldehyde) and to Cbz-Leu-Leu-Leu-aldehyde, and an example of its further optimization.

THF and DME are slightly polar solvents which are moderately good cation solvators. Coordination to the metal cation involves the oxygen lone pairs. These solvents, because of their lower dielectric constants, are less effective at separating ion pairs and higher aggregates than are the polar aprotic solvents. The crystal structures of the lithium and potassium enolates of methyl /-butyl ketone have been determined by X-ray crystal-... 

Fig. 1.3. Crystal structure of dimer of lithium derivative of TV-phenyl imine of methyl /-butyl ketone. (Reproduced with permission from Ref. 72. Copyright 1986 American Chemical Society.)...

A number of kauranoid diterpenoids have been isolated from the liverworts. (16i )-ent-Kauran-15-one, ent-15a-hydroxykaur-16-ene, and the corresponding 15-ketone have been isolated from the liverwort Jungermannia infusca and (16i )-ent-18-hydroxykauran-15-one, ent-kaur-16-en-18-oic acid, and ent- a-hydroxykaur-16-en-15-one have been found in another species, Porella densi-folia. The full paper on the crystal structure of enf-1 la,15or-dihydroxykaur-16-ene, which has been obtained from Jungermannia sphaerocarpa and Solenostoma trista, has appeared. ... 

Williams group observed low enantioselectivities for the Michael addition of a prochiral nucleophile, ethyl 2-cyanopropionate 623, to methyl vinyl ketone 624 catalyzed by chiral platinum complexes (Scheme 8.196)." The NMR analysis indicated that these cationic Pt complexes act as Lewis acids toward nitriles. The X-ray crystal structure as well NMR analysis showed that the solvent ligand that is readily displaced by an organic substrate is situated cis to the nitrogen donor in the Pt complex and, therefore, is in a chiral pocket created by the oxazoline ring. 

Rehse PH, Steinmetzer T, Li Y, Konishi Y, Cygler M. Crystal structure of a peptidyl pyridinium methyl ketone inhibitor with thrombin. Biochemistry 1995 34 11537-11544. 

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