LHASA

The only other times that the chemist must communicate with LHASA are when decisions are to be made about which structure is to be analyzed and what method is to be sed. In all cases a table of choices (or menu) is displayed and the chemist merely points to the one (or ones) that he wishes. A sample menu is shown below. 

SINGLE GROUP FULL SEARCH BOND MODE 

GROUP PAIR FULL SEARCH BOND MODE NARROW MODE MANUAL MODE 

APPENDAGE CHEMISTRY RING APPNDG ONLY BRANCH APPNDG ONLY 

KEY SUBSTRUCTURES DIELS-ALDER ROBINSON 44-2 ROBINSON f5 SMALL RINGS STEREOSPBCIFIC C=C 

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Early implementations of the CIP rules for computer detection and specification of chirality were described for the LHASA [105], CHIRON [106], and CACTVS [107] software packages. Recently, several commercial molecular editors and visualizers (e.g., CambridgeSoft s ChemOffice, ACD s I-Lab, Accelrys WebLab, and MDL s AutoNom) have also implemented the CIP rules. 

The use of computers for the design of chemical syntheses was first demonstrated by Corey and Wipke in 1969 with their program OCCS [30]. The successor to OCCS, LHASA [31], is generally considered to be the first synthon-based system. Its development is still going on. Currently, three groups are working on LHASA, one at Harvard University, USA [32], one at the University of Leeds, UK [33], and... 

Current research in LHASA is focused on developing new methods assisting users in choosing the most appropriate strategy for their target structures. Furthermore, the development of criteria for the evaluation of synthesis routes and/or algorithms for selecting optimal synthesis routes within the tree are discussed [34]. 

P2] LHASA Group homepage, http //lhasa.harvard.edu/... 

Ott M. A., Noordik J. H. Long-Range Strategies in the LHASA Program The Quinone Diels-Alder Transform J. Chem. Inf. Comput. Sci. 1997 37 98 108 Keywords computer application, quinone Diels-Alder transformations... 

M.A. Ott and J.H. Noordik, Long-range strategies in the LHASA program the Quinone Diels-Alder transform. J. Chem. Inf. Comput. Sci., 37 (1997) 98-108. 

In 1969 Corey and Wipke [7] reported the program OCSS (Organic Chemical Simulation of Synthesis) which was the precursor of one of the most powerful programs known at present which has been named LHASA (the acronym of Logic and Heuristics Applied to Synthetic Analysis) [5b] [8]. Since then, different... 

Although the philosophy of CHAOS is the classical one and very similar to that of other programs which work with a "database" (LHASA, SECS, MARSEIL, etc.), the difference lies in the fact that the "substructures" and the corresponding "disconnection tables" are not in a separate "database", but are an integral part of the program itself. This allows fast access to the necessary information. However, the major novelty of CHAOS is, perhaps, the way in which the "substructures" have been organised for access to them. 

Process automatically the structure of the alkaloid porantherine, first with the "default-order" of disconnections and then giving priority to "consonant" over "rings" disconnections. In the latter case you should "Save" only the intermediate precursors leading to the same synthetic sequence and the same starting material (A) used in Corey s synthesis, which was actually found by LHASA (see ref. 19, Chapter 12). 

LHASA Limited, Department of Chemistry, University of Leeds, Leeds, LS2 9JT, UK. 

A number of approaches are available or under development to predict metabolism, including expert systems such as MetabolExpert (Compudrug), Meteor (Lhasa), MetaFore [42] and the databases Metabolite (MDL) and Metabolism (Synopsys) [43]. Ultimately such programs may be linked to computer-aided toxicity prediction based on quantitative structure-toxicity relationships and expert systems for toxicity evaluation such as DEREK (Lhasa) (see also Chapter 8) [44]. 

LHASA Organic synthetic route design www.chem.leeds.ac. uk... 

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