**7. References**


It should be noted that the primary interaction between the enantiomers attached on the SAMs and prenucleation aggregates formed in solution is due to hydrophobic bonding or Van der Waals interaction. It is assumed that crystal growth proceeds only when the chirality of the prenucleation aggregate of pure enantiomers formed in solution is the same as that of the attached enantiomer. In racemic solution, on the contrary, most of the prenucleation aggregates are considered to be in DL-form, resulting in the growth of the

In this book chapter the preparation, structure, properties and applications of self-assembled monolayers (SAMs) in crystallization processes have been briefly reviewed. We have reviewed a variety of applications of SAMs in crystallization which can be catalogued into either pure crystallization methods or through the expression of chiral molecular

Although two decades have passed since the discovery of SAMs, it is still a very active and broad research area that is almost impossible to review comprehensively. The fundamental questions of adsorption, structure, phases, and phase transitions have been thoroughly studied in the past, but still several issues remain unresolved. A large part of present and future work is aimed at the modification and fictionalization of surfaces by SAMs for different applications, with molecular and biological recognition being the most dynamic. Since SAMs are not so much a specific class of compounds, but rather a very flexible concept with virtually unlimited potential for applications, we expect that the area of SAMs will

M. Ejgenberg would like to acknowledge the BIU President's scholarship and the ministry of science and technology program for the promotion of women in science and technology for

Addadi, L., Weinstein, S., Gati, E., Weissbuch, I., & Lahav, M. (1982). Resolution of

Banno, N., Nakanishi, T., Matsunaga, M., Asahi, T., & Osaka, T. (2004). Enantioselective

leucine molecules. *Journal of the American Chemical Society*, Vol. 126, 428-429

silver. *Journal of the American Chemical Society*, Vol. 121, 4500-4509

conglomerates with the assistance of tailor-made impurities. Generality and mechanistic aspects of the "rule of reversal". A new method for assignment of absolute configuration. *Journal of the American Chemical Society*, Vol. 104, 4610-4617 Aizenberg, J., Black, A.J., & Whitesides, G.M. (1999). Control of crystal nucleation by patterned self-assembled monolayers. *Letters to Nature*, Vol. 398, 495-498 Aizenberg, J., Black, A.J., & Whitesides, J.M. (1999). Oriented growth of calcite controlled by

self assembled monolayers of functionalized alkane thiols supported on gold and

crystal growth of leucine on a self assembled monolayer with covalently attached

racemic crystalline phase on both D and L-leucine attached SAMs.

**5. Conclusions** 

interactions of SAMs.

continue to prosper.

funding.

**7. References** 

**6. Acknowledgment** 


**3** 

*Chiba University* 

*Japan* 

**Asymmetric Reaction Using Molecular Chirality** 

Organic crystals have been utilized by organic chemists to identify materials by comparing melting point and mixed melting with known compounds, and to obtain pure materials by recrystallization. Furthermore, many attractive aspects of the crystals have been discovered since the latter half of the 1960's. For example, when organic molecules aggregate and form a crystal, a new property such as the electric conductivity or nonlinear optics characteristic develops by forming a peculiar arrangement style, and these crystals are used as electronic and optical materials. In addition, chemistry using the key information recorded in the molecule in the crystal has been developed. Molecular motion, which was cluttered with a variety of conformations in solution, is considerably controlled in the crystal, and molecules are arranged in a specific conformation depending on the closest-packing and molecular interactions in many cases. Therefore, a different molecular conformation will often be afforded in the crystal and in solution. In some cases, information for chirality recorded in the crystal is particularly interesting.1) Conglomerate crystals (racemic mixture) afforded from racemic compounds are also chiral crystals, which are used for preferential crystallization for optical resolution of racemate.2) On the other hand, compounds with unstable axial chirality, even in achiral in solution, may provide an axial chirality in a crystal where the molecular arrangement and molecular conformation are controlled. Using the chiral properties of the crystal, asymmetric synthesis without an external chiral source from achiral substrates has been studied by many research groups. This approach is also broadly

Since the 1970's, the combination of chiral crystallization and the solid-state photoreaction has provided many successful examples of absolute asymmetric synthesis.3) In these reactions, achiral materials adopted chiral arrangement only by spontaneous crystallization, and optically active products are obtained from the topochemically controlled reaction with high enantiomeric excesses (Figure 1).4) This method incurs a problem in the crystallization of achiral molecules in chiral space groups, albeit rare and unpredictable. However, in recent years, crystal engineering and the solid-state reaction to a variety of new systems has progressed to such an extent that it can now be regarded as an important branch of organic chemistry. Furthermore, some unique ideas involving solution chemistry utilizing the chiral crytals have also been developed. The achievement of an asymmetric synthesis starting from an achiral reagent and in the absence of any external chiral agent has long been an

**1. Introduction** 

recognized as an absolute asymmetric synthesis.

**Controlled by Spontaneous Crystallization** 

Masami Sakamoto and Takashi Mino

the precipitation of the least stable β form of Glycine. *Angewandte Chemie International Edition*, Vol. 44, 3226-3229

Yokota, M., Doki, N., & Shimizu, K. (2006). Chiral separation of a racemic compound induced by transformation of racemic crystal structures: DL-Glutamic acid. *Crystal Growth & Design*, Vol. 6, No. 7, 1588-1590
