Chiral prism

Recrystallization of the achiral oxo amide /V,/V-diisopropylphenylglyoxylamide (la) from benzene gave colorless chiral prisms [1], Each crystal is chiral and shows a CD spectrum in Nujol mulls (Fig. 1). One type of chiral crystal shows a (+)-Cotton effect and the other type shows a (-)-Cotton effect (Fig. 1). Crystals of (+)-la and (-)-la can easily be prepared in large quantities by seeding with finely powdered crystals of (+)-la or (-)-la during recrystallization of la from benzene. Measurement of the CD spectrum of chiral crystals as Nujol mulls is now well established [2],... 

Recrystallization of the achiral oxo amide MAf-diisopropylphenylglyoxylamide (78a) from benzene gave colorless chiral prisms. Each crystal is chiral and shows... 

Recrystallization of 96 from benzene afforded colorless prisms. That each crystal is chiral was shown by photochemical conversion into the optically active 97. Crystals of 96 which gave (+)- and (—)-97 on photocyclization have been tentatively identified as (+)- and (—)-crystals of 96, respectively. Large amounts of the (+)- and (—)-crystals of 96 can easily be prepared by seeding with finely powdered (+)- and (—)-... 

Self-assembled hexanuclear arene ruthenium metallo-prisms with 2,4,6-tripyridyl-l,3,5-triazine (ppt) subunits showed unexpected double helical chirality <06CC4691>. 

Recently, Sato and Hatano 67 69) found a new type of chiral lyotropic mesophase composed of Tween 80, sorbitan mono-9-octadecenoate poly(oxy-l,2-ethanediyl), and water, and discussed the ICD of achiral solute molecules intercalated into the lyotropic mesophase. As the concentration of Tween 80 is increased, three distinct phases are obtained micelle, neat phase, and reversed micelle, in that order. In the region of the volume ratio of Tween 80/(Tween 80 + water) of 0.40 to 0.63 under crossed Nicol-prisms, a focal conic texture was observed. This result indicates that the... 

The inversion of the N-atoms in the diethylenetriamine backbone is precluded. The central N-atom is always chiral, since the ethylene bridges around it have different conformations (<5 and A). Furthermore, the two other N-atoms are chiral as well in the bisamides and chirality of the metal ion should be taken into account. DTPA derivatives with three chiral N-atoms can be wrapped around the Ln3 + ion in 16 different ways (8 diastereomeric pairs, see Fig. 1). In crystal structures of these compounds the Ln3+ coordination polyhedron can generally be best described as a tricapped trigonal prism (TTP). For [Ln(DTPA)]2-A1=A2=A3 = B1=B2, and, consequently, only two enantiomers remain (1/1 ). Analogously, it can be seen that the DTPA-bisamides can have 4 diastereomeric pairs. 

Scheffer et al. provided another unimolecular asymmetric transformation involving the Norrish type II reaction, a well-known excited state process of ketones that is initiated by an intramolecular hydrogen atom transfer from carbon to oxygen through a six-membered transition state (Scheme 5). [19a] An adamantyl ketone derivative 27 was found to crystallize from ethanol in very large prisms in the chiral space group P2 2 2. Upon irradiation of these crystals to approximately 10% conversion, the chiral cyclobutanol derivatives 28 were afforded as the major products in 80% ee. 

Absolute asymmetric synthesis was observed in the solid-state photoreaction of benzoylbenzamide 59 to phthalide 60 however, the reaction mechanism was completely different from that of thioester 57. [35] Recrystallization of these amides 59a-c from the chloroform-hexane solution afforded colorless prisms in all cases. X-ray crystallographic analysis revealed that all prochiral amides 59a-c adopted orthorhombic chiral space group P2 2 2 and were frozen in chiral and helical conformation in the crystal lattice. 

Among other coordination spheres which may be chiral, there is the trivial case of the cA-hw-bidentate octahedral systems such as ciy-[Co(en)2Cl2], 6is-bidentate tetrahedral [M(A-A)2] or Z A-tridentate octahedral [M(A-A-A)2] complexes where the dihedral angle between the two chelate planes is different ih>m 90°, as is often the case. An example, together with the tns-tridentate [M(A-A-A)3] tricapped trigonal prism geometry often found for lanthanide complexes, is shown in Figure... 

Preparation of enantiomerically active hydrocarbons is difficult and only a few examples of the preparation of chiral hydrocarbons have been reported. For example, chiral 3-phenylcyclohexene has been derived from tartaric acid through eight synthetic steps. Enantiomeric separation by host-guest complexation with a chiral host is more fruitful for the preparation of chiral hydrocarbons. For example, when a solution of fR,Rh( )-t ws-4,5-bis(hydroxydiphenylmethyl)-l,4-dioxaspiro[4.4]-nonane (lb) [2] (3 g, 6.1 mmol) and rac-3-methylcyclohexene (2a) (0.58 g, 6.1 mmol) in ether (15 ml) was kept at room temperature for 12 h, a 2 1 inclusion complex of lb and 2a (2.5 g, 75%) was obtained as colorless prisms in the yield indicated. The crystals were purified by recrystallization from ether to give the inclusion complex (2.4 g, 71%), which upon heating in vacuo gave (-)-2a of 75% ee by distillation (0.19 g, 71%) [3]. By the same inclusion complexation, (-i-)-4-methyl- (2b) (33% ee, 55%), (-)-4-vinylcyclohexene (2c) (28% ee, 73%), (-)-bicyclo[4.3]-nonane-2,5-diene... 

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