Increasingly, patents have been issued with claims to chemical substances that
differ little from known compounds - specific salts, stereoisomers, purified
versions of compounds known to exist in impure form. The standard for
patentability is, as always, that the claimed substance has never been reported
and that the new substance has new and unexpected properties when compared with
the known analogs. If, in fact, the keto tautomer is isolated as a single
entity and not as a component in an equilibrium mixture with the enol, that
should be enough to confer patentability.
If the patent has been granted on the basis of unsupported claims, which has
happened in some cases of stereoisomers and salts, there is a possibility that
the patent claims wouldn't survive opposition or an invalidity lawsuit.
There are other kinds of patent claims that would appear to be less vulnerable.
Claims for methods of isolating the tautomer, new uses or compositions, or uses
and compositions for which the enol would be unsuitable should be patentable
regardless of the fact that the equilibrium mixture was known.
Edlyn Simmons
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From: Robert Buntrock <buntrock2@earthlink.net> on 10/03/2000 02:20 PM
To: Gerben Gieling <chem@synthon.nl>
cc: piug-l@derwent.tecc.co.uk (bcc: Edlyn Simmons-ES/PGI)
Subject: Re: Keto-Enol
>From a chemical standpoint, if the both the enol and keto forms are
stable (isolable, etc.), each should be patenable. Stable enol forms of
ketones and amides do exist, especially in heterocyclics. However, the
keto-amide form of hyroxypyridines, etc., has been determined in recent
decades to be the more stable form, although the hydroxyimine form is
easier to name.
I'll leave it to the patent agents/attorneys to decide if that's enough
reason to patent each isomer.
-- Bob Buntrock
Buntrock Associates, Inc.
(usual disclaimers, esp. in re legal opinions)
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