# T17-2026 - BIOVIA Chemical Registration: R/S enantiomers may be incorrectly registered as lots of the same concept

A rare case was observed where two enantiomers of a large structure, with a wide variety of tetrahedral stereo centers, were classified as duplicates in Chemical Registration. The two enantiomers were presented to the registrar as duplicates, so that enantiomer A could be registered as lot to the concept record of enantiomer B.

## Program

BIOVIA Chemical Registration

## Operating System

All supported operating systems

## Description

A rare case was observed where two enantiomers of a large structure, with a wide variety of tetrahedral stereo centers, were classified as duplicates in Chemical Registration. The two enantiomers were presented to the registrar as duplicates, so that enantiomer A could be registered as lot to the concept record of enantiomer B.

Detailed investigations have shown that this was caused by a timeout of the matching procedure (“flexmatch”) in the BIOVIA Direct Oracle cartridge. The Direct cartridge uses a standard timeout behavior, in which flexmatch queries return the value 1 when a timeout occurs. Consequently, in our case, the two stereoisomers were identified as matching.

## Resolution

Administrators of BIOVIA Chemical Registration installations can change the standard timeout behavior of the Direct cartridge by customizing the “Find Duplicate Structures” extension as shown on the following picture. A flexmatch flag ALLOW\_TIMEOUT is added to the flexmatch queries for exact matches and for tautomers and stereoisomers.

Note that setting the ALLOW\_TIMEOUT flag does not change the matching behavior. It only changes the return value in cases of timeouts from 1 to 0.

![Screenshot](https://www.3ds.com/assets/invest/inline-images/t17-2026-screenshot.png)If you believe you are affected please contact BIOVIA Support including any of these references: REG-22947or DIR-4339.

## How to contact BIOVIA Support

If you have any questions, please contact [BIOVIA Support](https://www.3ds.com/support/contact-your-support-center#Brick-ff51f59f-40eb-46fa-9d58-5499b06ecfd2).

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