SECS program

At this stage in the program s development, it is appropriate to report our experiences in implementing, evaluating and enhancing the SECS program at Merck, and to review plans for future development. 

Module Table I SECS Program Modules Description... 

SYNCOM Stand-alone program for converting descriptions of chemical reactions written in ALCHEM into an object code usable by the SECS program. 

SECS program from 240 K bytes (48 K words) on the PDP-10 to approximately 620 K bytes on our IBM 370/168 computer. This does not present a problem, however, since under IBM s virtual operating system,(U) each application program has available 16,000 K bytes of storage. 

Implementation Problems. A discussion of problems encountered during implementation of the SECS program follows in three parts problems in converting the assembly language... 

Bit by bit comparison except for floating point variables whose fractions both evaluate as zero. (Refer to text for consequences in SECS program.)... 

It was widely believed that such a detailed course was not necessary for learning how to operate the SECS program. 

Our experiences in using the SECS program indicated that further development was necessary for SECS to become routinely useful to the synthetic chemist. While development of new program features and strategies was deemed essential, these tasks have so far been left mainly in the hands of Professor Wipke s research group. We at Merck have concentrated on a different task expanding and correcting the base of chemical... 

ALCHEM.J ) This was designed to allow simple chemical statements to access all of the perceived structural information in the SECS program. An example of a statement is ... 

SECS program improvements must occur in several areas. We hope to implement an up-to-date version of SECS at Merck, to overcome many present limitations. In addition, high-level strategies must be developed to guide analyses, especially as the reaction data base expands, in order to remove uninteresting precursors and keep to a reasonable size the total number of structures generated. While our experience may help define successful strategies, this is not the area of Merck s initial interest. 

Different releases of the SECS program are identified by different version numbers, starting with 1.0. The current release of the program corresponds to version 2.7. 

Temperature Programmed Oxidation. These measurements characterize both the amount and chemical nature of the carbon on the surface. After a surface is exposed to ethylene and pretreated as desired, it receives a 6 L dose of O2 at 323 K. The TPO spectrum is the CO desorption signal at a 6 K/sec programming rate. CO2 accounts for less than 1% of the oxidation, so the CO signal accounts for essentially all of the carbon removed. O2 dosing is repeated until no further CO is evolved during heating. SIMS results show that all carbon has been removed from the surface at the TPO end point. 

Ocean Circulation Experiment) tritium/helium isotope survey exceeds that achieved during the GEO SECS program by a factor of 10. The data density obtained from this survey is sufficiently high to allow 3-dimensional visualizations of the tritium plumes in the ocean. In this way, the WOCE tritium/ He sections (for an example, see Fig. 4)... 

Figure 1. Gas chromatograms from a Freon 113 extract of Concord grape juice concentrated 3,500 times (top) and the 3% ether-pentane fraction of a Florisil separation of the whole Freon 113 extract concentrated 13,000 times (bottom). The dots show regions where odor was detected. Conditions 30 m 0.3 mm carbowax 20 M column, helium gas flow of 23 cm sec programmed...

All functions of the SECS program can also be invoked from a teletype device or alphanumeric CRT terminal. Structural input of 1 from the teletype is illustrated by the dialog in Figure 2. 

For a synthesizer, we are reimplementing the Simulation and Evaluation of Chemical Synthesis (SECS) program on our IBM computer in collaboration with Professor Wipke, Once the program is running at Merck, we will instruct the chemists in program operation, and then ask them to code and test transforms. 

Several programs allow a more detailed description including stereochemistry. In this case, more information is necessary to describe the position of atoms in space. To describe the atoms at a chiral carbon atom, in Wipke s SECS program, the list of attached atoms is ordered so that viewing down the bond from the first atom of the list to the central atom, the other... 

The Standard Molecular Data (SMD) format is designed to provide such an integration tool on the basis of a file format. It has been developed in the course of the CASP project (Computer Assisted Synthesis Planning) which is run by a consortium of seven German and Swiss Chemical Companies (BASF, Bayer, Ciba-Geigy, Hoechst, E Merck, Hoffmann La Roche and Sandoz). The basis of this development was the Molfile format of the earlier SECS program (4) (Simulation and Evaluation of Chemical Synthesis). 

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