Appeal No. 2006-0881
Application No. 09/928,139
acid.1 The resulting mixture is then treated whereby the threo stereoisomers are enriched over
the erythro stereoisomers followed by separation of the erythro stereoisomers to leave a mixture
of d-threo-methylphenidate and l-threo-methylphenidate enantiomers for resolution. This
appealed subject matter is adequately represented by independent claim 1 (the sole independent
claim on appeal) which reads as follows:
1. A process for obtaining single enantiomer d-threo-methylphenidate or l-threo-
methylphenidate, which comprises resolution of a mixture of the d-threo-methylphenidate and
l-threo-methylphenidate enantiomers; racemisation of the unwanted enantiomer, to give a
mixture of all four stereoisomers, wherein the racemisation comprises reacting the unwanted
enantiomer with an acid; enriching said mixture following racemisation wherein the d-threo and
l-threo stereoisomers of methylphenidate are enriched over the d-erythro and l-erythro
stereoisomers of methylphenidate; and separation of said d-erythro and l-erythro stereoisomers,
to leave the said mixture of d-threo-methylphenidate and l-threo-methylphenidate enantiomers
for resolution.
The references set forth below are relied upon by the examiner in the § 103 and
obviousness-type double patenting rejections before us on this appeal2:
1 According to the appellants, methylphenidate has two chiral centers, and any compound having two chiral centers
will theoretically yield a racemate containing four separate isomers. The appellants further explain that it was
known in the prior art to racemize methylphenidate wherein one of the two chiral centers became racemized to
thereby yield two isomers (i.e., a mixture of the stereoisomers). However, it is the appellants’ position that, prior to
their invention, it was not known how to racemize both chiral centers of methylphenidate.
2 In the answer, the examiner has referred to newly cited references (i.e., the Gao, Beausoleil, and Shimoju
references; see pages 6 and 14 of the answer) as supporting her obviousness position even though these references
are not included in the examiner’s statements of her rejections. If these references are meant to support the
proposition that compounds having two chiral centers are theoretically capable of being racemized to yield four
isomers as indicated in the paragraph bridging pages 13-14 of the answer, then no such support is necessary
particularly since the proposition has not been denied by the appellants (e.g., see the paragraph bridging pages 9 and
10 of the supplemental brief). On the other hand, if these newly cited references are relied upon for supporting the
examiner’s obviousness conclusions, then the references should have been positively included in the examiner’s
statements of her rejections. See In re Hoch, 428 F.2d 1341, 1342 n.3, 166 USPQ 406, 407 n.3 (CCPA 1970). Also
see the Manual of Patent Examining Procedures (MPEP) § 706.02(j) (Rev. 3, August 2005) and § 2144.08 (id.).
2
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