DRAW BASIC 7.0 command

This tutorial, which is based on the Beilstein update BS0202PR (May, 2002) and on the retrieval program Cro.ssFire Commander V6,. shows. some typical advanced search examples in the Beilstein database. It is assumed that the user already knows some of the basic features of the retrieval program. Moreover, in this tutorial the CrossFire Structure Editor is used instead of the (SIS/Draw Structure Editor. The first example is a combined application of structure aiM fact retrieval, whereas the second example demonstrates reaction retrieval. 

The four Build Menus in REACCS are Structure, Query, Top, and HighlightRxn. Structure menu contains the basic drawing commands used to construct the backbone of the structure. Query menu contains the commands used to add flexible structural parameters to the query. Top menu contains commands used to build reactions and to store and retrieve reactions, molecules, and graphic queries. HighlightRxn menu contains commands that apply atom/atom mapping and reaction centers to the current reaction. Atom/atom mapping is used to identify the reaction centers and increase accuracy and efficiency by letting the searcher specify that a particular atom in a reactant must correspond to a particular atom in the product. 

Pericyclic reactions can proceed under acidic or basic conditions. For example, the oxy-Cope rearrangement is greatly accelerated under basic conditions, and the Diels-Alder reaction is greatly accelerated by Lewis acids. Often a series of polar reactions is used to synthesize an unstable intermediate, which then undergoes a pericyclic reaction to reveal the product. In other words, a good command of polar mechanisms (Chapters 2 and 3) is essential to understanding how to draw pericyclic mechanisms. 

An example should make this clear. Suppose the screen allowed 40 pixels in the horizontal direction and 48 pixels in the vertical direction. Suppose that a version of BASIC had line-drawing commands as follows ... 

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