Notations, ROSDAL

In Sections 2,.3.1-2.3.4, only the four most popular line notations, Wiswesser (WLN), ROSDAL. SMILES, and Sybyl (SEN), arc discussed. Whereas WLN is now almost obsolete, SMILES is quite an important representation and is widely used (Figure 2-7). 

The ROSDAL (Representation of Organic Structures Description Arranged Linearly) syntax was developed by S. Welford, J. Barnard, and M.F. Lynch in 1985 for the Beilstein Institute. This line notation was intended to transmit structural information between the user and the Beilstein DIALOG system (Beilstein-Ohlme) during database retrieval queries and structure displays. This exchange of structure information by the ROSDAL ASCII character string is very fast. 

The ROSDAL syntax is characterized by a simple coding of a chemical structure using alphanumeric symbols which can easily be learned by a chemist [14]. In the linear structure representation, each atom of the structure is arbitrarily assigned a unique number, except for the hydrogen atoms. Carbon atoms are shown in the notation only by digits. The other types of atoms carry, in addition, their atomic symbol. In order to describe the bonds between atoms, bond symbols are inserted between the atom numbers. Branches are marked and separated from the other parts of the code by commas [15, 16] (Figure 2-9). The ROSDAL linear notation is rmambiguous but not unique. 

Figure 2-9. A possible ROSDAL code for phenylalanine in a) a complete and b) a compressed notation.

Chemical structures can be transformed into a language for computer representation via line notations such as ROSDAL, SMILES, Sybyl. 

Figure 9.7. Various linear notation schemes for chemical representation. Some contain only atom types and connectivity (WLN, ROSDAL, SMILES, SLN) and are chemist-readable. Others are compressed versions of molecule file formats (CHIME) and are meant for computer interpretation.

ROSDAL. Linear notation scheme devised by the Beilstein Institute. It can contain just connection table information, or it may also contain atom coordinates. Several chemical information systems can convert ROSDAL strings to other structure file formats. 

Hie HOSE code represents a linear notation of a chemical structure. Other codes are ROSDAL, SYBYL, and SMILES. The latter code is currently the most popular linear notation. 

In this section the syntax which underlies the ROSDAL structure notation will be outlined. The ROSDAL system also provides for a flexible description of different kinds of substructures however, the main emphasis will be given to the... 

Various line notations have been devised to depict accurately both the atomic content and the orientation of the compound. Much of the focus in creating notation systems has been geared toward computer input and manipulation of structures. Some of the well-known notations include Wiswes.ser (WLN), Dyson-IUPAC, Hayward, Skolnik, Gremas and more recently also SMILES, and ROSDAL. All of these systems require a detailed memorization of their rules and conventions and are limited strictly to the audience familiar with those rules. 

Another linear notation is the ROSDAL coding. It has very elaborate stereochemical syntax elements, which make it useful for the definition of organic as well as inorganic compounds. It covers even conformation representations. ROSDAL strings are extensively used in the Beilstein XFIRE system. 

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