Steroidal Inclusion Crystals

Dynamics in Organic Inclusion Crystals of Steroids and Primary Ammonium Salts 505... 

We have researched the inclusion abilities of bile acid derivatives by using more than one hundred organic compounds as guest candidates. The inclusion phenomena vary from one case to another, indicating that subtle changes in molecular structures induce alteration in their molecular assemblies. In fact, X-ray diffraction studies prove that the steroidal hosts form various assemblies such as monolayers, bilayers, helical tubes, and so on, as shown in Figure 2. Therefore, systematic investigation of inclusion crystals of bile acid derivatives is expected to reveal a relationship between their molecular structures, assemblies and inclusion behavior. 

Lahav, Leiserowitz and their coworkers have used inclusion complexes of deoxycholic acid to carry out asymmetric photochemical reactions. The authors reported that acetophenone forms a 2 5 crystalline channel inclusion complex with deoxycholic acid 22 as the host and that irradiation of the complex in th4 solid state leads to abstraction of a hydrogen atom by the acetophenone 23a from C5 of the steroid followed by coupling of the resulting radical pair to produce1 photoproduct 24 (Scheme 9) [216,219]. The authors were able to follow the course of the reaction by x-ray crystallography. Only one diastereomer of the product was obtained in the reaction. Aoyama et al. have studied the reaction of AT,N-dialkylpyruvamides in deoxycholic acid inclusion crystals (Scheme 10) [246], Solid-state irradiation of the inclusion complex of 22 and 25 gave the... 

Organic inclusion crystals are attractive substances from the viewpoint of the dynamics of molecular assemblies. The inclusion crystals comprise nanocomposites between host and guest molecules and exhibit supramolecular properties through non-covalent bonds [1], The host molecules provide molecular-level cavities where the guest molecules undergo intercalations and reactions. We have elucidated such dynamics by using the inclusion crystals of steroids and primary ammonium salts (Figure 26.1). 

Figure 26.1 Dynamical properties related to organic inclusion crystals of steroids and primary ammonium salts.

Figure 26.5 Intercalation in sandwich-type inclusion crystals of steroidal cholic acid. Benzene derivatives undergo reversible desorption and absorption, accompanied by changes in bilayer distances.

Steroidal compounds have been shown to act as inclusion hosts. The Miyata group has made the development and interpretation of this chemistry very much their own through their skillful analysis of over 300 inclusion crystal structures. Concave face to concave face association by means of hydrogen bonding results in bilayer formation in many of these inclusion crystals, but a very wide range of different host-guest structural assembUes is possible. One crystal form of the compound (4) (ethyl acetate) is illustrated in Figure 2 ... 

Molecular architecture of steroidal acids and their derivatives selective acquisition of polymorphic inclusion crystal of cholic acid... 

The anaesthetic steroid 3a-hydroxy-5a-pregnane-ll,20-dione has normal conformational features, both in the crystal and in solution. X-Ray data show that deoxycholic acid can form an inclusion complex in which alternate molecules of dimethyl sulphoxide and water are held in canals formed by helically arranged host molecules.Six different crystalline forms of 17a-ethynyloestradiol have been recognized. X-Ray structural data are reported for 3-methoxy-2-aza-oestra-l,3,5(10)-trien-17/3-yl acetate, 3/3-hydroxypregn-5-en-20-one (pregnenolone), 5a-cholest-2-ene, 3/3-bromo- and 3/3-chloro-cholest-5-enes, and cholesteryl acetate (at 123 K), benzoate, chloroformate, ° laurate, methyl carbonate, and 24-norcholesteryl acetate. ... 

An X-ray crystal structure analysis of the complex shows that the tertiary 3-, 5-, and 20-hydrogens of the steroid in particular are exposed to the guest (1) in the inclusion channel. 

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