T 0552/91 (Chroman derivatives) of 3.3.1994

European Case Law Identifier: ECLI:EP:BA:1994:T055291.19940303
Date of decision: 03 March 1994
Case number: T 0552/91
Application number: 87118275.4
IPC class: C07D 405/04
Language of proceedings: DE
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Documentation of the appeal procedure can be found in the Register
Bibliographic information is available in: DE | EN | FR
Versions: OJ
Title of application: -
Applicant name: MERCK PATENT
Opponent name: -
Board: 3.3.01
Headnote: 1. Where a European patent application relates to chemical substances originally defined by an incorrect chemical structural formula, correction of which is not allowable under Rule 88 EPC, replacement of the incorrect formula by the correct one infringes Article 123(2) EPC. This applies even if evidence is provided that these substances are the inevitable unambiguous result of a method disclosed in full in the application as filed (points 4.2 and 4.3 of the reasons).
2. Nevertheless, the submission of a "product-by-process" claim is compatible with Article 123(2) EPC if it contains all the measures required to obtain this result (starting materials, reaction conditions, separation) (point 5.2 of the reasons).
Relevant legal provisions:
European Patent Convention 1973 Art 84
European Patent Convention 1973 Art 123(2)
Keywords: Amendment of a structural formula subsequently found to be incorrect (no)
Product-by-process claims (allowed)


Cited decisions:
G 0003/89
T 0012/81
T 0514/88
Citing decisions:
T 0333/93
T 1074/97
T 0569/99
T 0956/04
T 2003/07
T 2285/09
T 0863/12

Summary of Facts and Submissions

I. European patent application No. 87 118 275.4 was filed on 10 December 1987 and published as EP-A-273 262. The application contained eight claims, the first of which related to chroman derivatives of general formula I,

Formula I

where the radicals R1 to R4 , R6 and R7 had different meanings which are of no relevance to the facts to be decided here. R5 represented a 1H-2-pyridon-1-yl, 1H-6-pyridazinon-1- yl, 1H-2-pyrimidinon-1-yl, 1H-6-pyrimidinon-1-yl, 1H-2- pyrazinon-1-yl or 1H-2-thiopyridon-1-yl radical unsubstituted or mono- or disubstituted with A, F, Cl, Br, I, OH, OA, OAc, NO2 , NH2 , AcNH, COOH, and/or COOA, whereby these radicals could also be partially hydrogenated, A was alkyl with one to six C atoms and Ac was alkanoyl with one to eight C atoms or aroyl with seven to eleven C atoms. Claim 3 related to a method for producing compounds of general formula I, which - insofar as it is of relevance here - was characterised in that a 3,4-epoxychroman of formula II

Formula II

was reacted with a compound of formula III

R5-H (III)

or one of its reactive derivatives. The other claims are of no importance here. Almost two years after the application was filed, the applicant established by means of X-ray structural analysis that when those starting materials of formula III containing a hydroxy substituent are reacted with compounds of formula II, it is not the corresponding compounds of formula I which are produced, but isomers of formula I',

Formula I'

where R5''' is a 1H-2-pyridonyl-, 1H-6-pyridazinonyl-, 1H-2- pyrimidinonyl-, 1H-6-pyrimidinonyl-, 1H-2-pyrazinonyl- or 1H- 2-thiopyridonyl-radical (bound to the oxygen atom through a ring C atom). To take account of this fact, when the applicant submitted amended claims 1 to 17 on 9 March 1991 it did not request any changes in the structural formula to this effect, but deleted from the substance claims the group of substances with the incorrect formula and characterised the claimed products by process features in new claims 10 to 17. Independent claim 10 related to all chroman derivatives obtainable by the above-mentioned essential reaction step described in original claim 3. Independent claim 11 was likewise a "product-by-process" claim, which was however directed only to the compounds already mentioned, whose structure had subsequently turned out to be incorrect. Claims 12 to 17 related to individual compounds characterised by the indication of the starting materials of formulae II and III required for their production and their melting point.

II. After the examining division of the European Patent Office had informed the applicant that in its opinion the amended application did not comply with the requirement laid down in Article 123(2) EPC, it rejected the application in its decision dated 26 April 1991 because claims 10 to 17 were not derivable from the content of the application as filed, which only covered substances of formula I. Those compounds having a different structure to that originally assumed were to be regarded as extensions of the subject-matter of the initial disclosure, to which claims cannot be directed even indirectly through "product-by-process" claims. Furthermore, the conditions for correction of the original documents under Rule 88 EPC had not been met. In addition, characterising the claimed compounds by their production method was at variance with the requirements of Article 84 EPC, as the claims neither defined clearly the matter for which protection was sought, nor were they supported by the description. This also applied to the subject-matter of claims 12 to 17 directed to individual compounds with specific melting points, since the original documents did not indicate in full a single method for producing such compounds; all that could be inferred from the description was that these substances were obtained "analogously" to the production of compounds of formula I.

III. An appeal, accompanied by a statement of the grounds, was filed against this decision on 27 June 1991 and the prescribed fee was paid at the same time. The statement of grounds explained that there was no doubt that, by disclosing the production method, the application had made available to the skilled person new compounds extending beyond the scope of claim 1 so that it was only necessary to examine how this part of the invention could be defined. "Product-by-process" claims were appropriate for this purpose. There could also be no objection to claims 12 to 17, as the starting materials mentioned in them could be readily inferred from the original documents.

IV. Oral proceedings took place on 3 March 1994. At the beginning of the proceedings the board voiced its preliminary opinion concerning the conditions under which patent protection could be obtained for substances whose structure had not initially been correctly indicated.

In the course of the oral proceedings the appellant submitted a set of amended claims 1 to 17. Claims 1 and 4 merely contained editorial amendments to the version on which the contested decision had been based; furthermore, claim 10 of the latter version was deleted to take account of the board's objection to the insufficiently concise claims (Article 84 EPC). Claims 11 to 17 were renumbered 10 to 16 and supplemented. In addition, a new claim 17 was submitted, in which the group of substances whose structure had originally been incorrectly stated was characterised by the amended general formula I'. Claim 10 is now directed to

"chromanol or chromene derivatives, obtainable through reaction of an epoxychroman of formula II according to claim 3 (see point II above) with a compound of formula III'

R5''-H (III')

where R5'' is a hydroxy-substituted 1H-2-pyridon-1-yl, 1H-6- pyridazinon-1-yl, 1H-2-pyrimidinon-1-yl, 1H-6-pyrimidinon-1- yl, 1H-2-pyrazinon-1-yl or 1H-2-thiopyridon-1-yl radical, these radicals being optionally substituted with a further radical A, F, Cl, Br, I, OH, OA, OAc, NO2, NH2, AcNH, COOH or COOA and/or partially hydrogenated, A and Ac having the meanings given in claim 1 (see point I above), or with one of its salts in the presence of a base and an inert solvent, subsequent usual processing and chromatographic separation of chromene from chromanol."

Claim 11 relates to a chromanol derivative of mp 262 - 265°C, obtainable by reacting 2,2-dimethyl-3,4-epoxy-6-cyanochroman with 3-hydroxy-1H-2-pyridone in the presence of sodium hydride in dimethyl sulphoxide, usual processing and chromatographic separation of the corresponding chromene in silica gel with dichloromethane.

Claims 12 to 16 relate to other individual compounds, characterised in corresponding manner.

Claim 17 is directed for the first time to chroman derivatives of formula I' (see point I).

The appellant submitted that the processes according to claims 10 to 16 as now worded unambiguously led to the substances of formula I'. Substances of formula I were only analytically proven, but were not formed in isolatable quantities, as was established in the subsequently published article in

(1) J. Med. Chem. 33 (1990), 2759 - 2767,

which was filed during the examination proceedings. The newly submitted claim 17 related to the same substances as the "product-by-process" claim 10, so that there was no difference between these claims as regards the requirement laid down in Article 123(2) EPC. If, therefore, the submission of claim 10 was admissible, this should likewise be the case for claim 17, even if the conditions laid down in Rule 88 EPC for correction of the general formula were not met. This was also consistent with German case law as, in the "cycloalkenes" decision (GRUR 1973, 313), the Federal Patent Court had allowed the correction, during the grant procedure, of a structural formula which had originally been incorrectly stated. Furthermore, claim 17 defined the matter for which protection was sought considerably more clearly than claim 10 and therefore complied better with the requirements of Article 84 EPC.

V. The appellant requests that the case be remitted to the examining division for resumption of the examination proceedings on the basis of claims 1 to 17 submitted during the oral proceedings (main request) and, in the alternative, on the basis of claims 1 to 16 (auxiliary request).

At the end of the oral proceedings, the board's decision to allow the auxiliary request was announced.

Reasons for the Decision

1. The appeal is admissible.

2. The examining division based its rejection of the application on the fact that, through the submission of "product-by-process" claims for the group of substances whose formula had been found to be incorrect in the course of the grant procedure, Article 123(2) EPC had been infringed. Furthermore, the board infers from the contested decision that there were also objections to these claims with regard to Article 84 EPC. These claims, albeit in amended form, have also been submitted to the board. In addition, an amendment was made for the first time during the appeal proceedings to the structural formula for that group of substances to which the originally assumed structure is not applicable. The only questions to be decided here thus relate to the admissibility of claims 10 to 17, as now worded, in view of the requirements of this Article.

3. In the board's understanding, the question arises here for the first time as to whether and in what form protection can be obtained for groups of chemical substances and individual compounds whose originally disclosed structural formula subsequently proves incorrect. The appellant attempts to secure such protection on the one hand by a further substance claim directed to the group of compounds with the structural formula subsequently found to be correct (main request) and, on the other, by "product-by-process" claims not containing the structural formula found to be incorrect (auxiliary request). In actual fact the main request would have to be rejected if only because, as the appellant has itself submitted, claims 10 and 17 relate to the same subject-matter, so that the set of claims as a whole cannot be regarded as concise within the meaning of Article 84 EPC. The board has refrained from requesting a rectification of this deficiency because the main request cannot be granted for another reason.

4. Main request

4.1 The main and auxiliary requests differ only in that the latter does not include claim 17. The board can therefore confine itself here to examining whether this claim is compatible with the provisions of Articles 84 and 123(2) EPC.

4.2 It may be that claim 17 complies better with the requirement of clarity (Article 84 EPC) than the corresponding "product-by-process" claim 10. Correcting the incorrect formula by submitting this claim may therefore seem desirable in the interests of legal certainty. As, however, the subsequent amendment of formula I, which led to formula I' in claim 17, cannot be regarded as rectification of an obvious mistake within the meaning of Rule 88 EPC, as the appellant conceded in the oral proceedings, it can only be allowed if it does not infringe Article 123(2) EPC, which likewise serves to safeguard legal certainty.

4.3 This provision stipulates that a European patent application may not be amended in such a way that it contains subject-matter which extends beyond the content of the application as filed. The board understands "content" to mean the entire technical disclosure derived by a skilled person from the application (see Singer, Kommentar zum EPÜ (1989), 591; T 514/88, OJ EPO 1992, 570, and also, in a different connection, G 3/89, OJ EPO 1993, 117, point 2 of the reasons). Furnishing proof that as a result of amendment of the original patent application nothing other than the originally disclosed subject-matter is claimed is therefore not enough to allow this amendment under Article 123(2) EPC. What is more important is that technically relevant information which the skilled person could not derive from the original documents is not thereby added to the application.

4.4 Claim 17 conflicts with this in that the subsequently amended general formula for the first time gives the skilled person crucial information about the true chemical structure of the group of substances and thus knowledge of the internal composition of the substances described therein. This leads to conclusions regarding their physical and chemical properties and those susceptible of industrial application. However, the information added to the application through the amendment of the general formula and relating to the true composition of the group of substances covered by claim 17 could not have been obtained from the application as originally filed in which these substances were given a different structure. Nor was this disputed by the appellant. Amending the application by incorporating claim 17 is therefore contrary to Article 123(2) EPC. For this reason the main request cannot be allowed.

4.5 In support of its differing opinion, the appellant refers in vain to German legal practice. Whilst the board is not convinced that a comparable practice also exists in the other EPC contracting states, it is aware that German practice differs from that of the EPO as regards amendments to the original application documents. Thus, the belated inclusion of equivalents, indications of advantages or examples, which is contrary to Article 123(2) EPC for the reasons given in point 4.3, is regarded as complying with the German Patent Law (see Schäfers in Benkard, Patentgesetz, 9th edition 1993, Section 38, point 19 ff.). Furthermore, the "cycloalkenes" decision cited in this connection is not concerned with whether the correction of a structural formula later found to be incorrect is possible within the context of a substance invention; it simply allows the inclusion of an amended structural formula in a claim relating to a method for producing chemical compounds, because the measures to be applied to obtain the process products, which alone are the subject of protection, are not thereby changed.

5. Auxiliary request

5.1 Apart from the title "Chromanol or chromene derivatives" - which, although general, is accurate - and the method of production, the application as filed contains no details which would help characterise more clearly and in an admissible manner those substances to be protected by claim 10 (see point IV). Similarly, the indication of the melting point and the appropriate general title in each case, together with the production measures in claims 11 to 16, ensures the greatest possible clarity within the bounds of what is admissible. The wording of claims 10 to 16 as "product-by-process" claims is therefore compatible with the requirement of clarity in Article 84 EPC.

5.2 The board infers from the contested decision the legal opinion that even if a "product-by-process" claim is submitted, no protection can be obtained for substances defined by a formula when their originally indicated structure subsequently turns out to be incorrect, because substances whose formula was originally not disclosed are thereby claimed implicitly. The result in such a case is that substance protection is generally unsuccessful because of the disclosure of an incorrect formula (which, under Rule 88 EPC, may not be corrected).

The board does not share this view as it disregards the fact that a substance claim is intended to protect the substance itself and not a formula. The latter serves merely to define the substance to be protected. If, therefore, the originally selected definition by a structural formula subsequently proves to be incorrect and the original documents contain other means of unambiguously characterising the disclosed substance, these can be used instead to formulate a claim directed to this substance. The prime example here is a method of production, which is in any case generally indicated in the original application to ensure that the substance invention is sufficiently disclosed. However, in such a case it is necessary to include in the claim all the process parameters required for defining unambiguously the claimed substances as inevitable process products (see T 12/81, OJ EPO 1982, 296, point 8 of the reasons). As chemical reactions only rarely take one particular course and therefore only rarely lead to uniform substances, it is generally necessary to indicate not only the starting materials and reaction conditions, but also the method by which the reaction mixture is processed to obtain the claimed substances, especially when, as in the case in question, their isolation is not possible because the correct structure of the products to be isolated cannot be given.

5.3 It is obviously harder to satisfy these conditions for claim 10 directed to a broad group of substances than for claims 11 to 16 relating to single compounds, which furthermore contain the melting point (indicated in the original application) as an additional parameter for characterising the claimed substances; this is because isolation measures, which unambiguously lead to specific single substances, do not necessarily have to be successful for all the individual components of a group of substances.

5.4 In the case in question, the board considers it plausible that the measures contained in claim 10 as now worded - ie the reaction of the epoxy chroman of formula II according to claim 3 with a compound of formula R5''-H (III'') or one of its salts in the presence of a base and an inert solvent and the subsequent usual processing and chromatographic separation of chromene from chromanol - inevitably lead to uniform products; in response to the board's enquiry as to whether compounds of the originally disclosed formula I were not after all produced as by-products of this process, the appellant referred to the paragraph bridging pages 2765 and 2766 of publication (1) - which was to be regarded as an expert report - and stated what was therefore irrefutable at the time, namely that such compounds were only formed in quantities which could be analytically detected but not isolated. The measures indicated above, and therefore their inevitable result, are disclosed in the original documents by claim 3 in conjunction with the description, page 6, lines 25 to 39, and page 8, lines 33 to 36, in conjunction with example 1. The term "reaction" in this connection clearly implies that this "product-by-process" claim comprises only chromanol or chromene derivatives in which the essential structural elements of formulae II and III'' are present. Claim 10 as amended is therefore compatible with Article 123(2) EPC.

5.5 With regard to claims 11 to 16 directed to individual compounds, the contested decision correctly established that the starting materials of formula III' referred to therein were not explicitly mentioned in the original description. However, the board is satisfied that they can be derived unambiguously from the details given in example 1 of the application as filed (see page 8, line 40, to page 11, line 53, of the published application, which corresponds in content with the original application). This first of all describes the reaction of 2,2-dimethyl-3,4-epoxy-6- cyanochroman with 1H-2-pyridone in dimethyl sulphoxide as a solvent in the presence of NaH and subsequent chromatography on silica gel with dichloromethane as an eluent, yielding two products: 2,2-dimethyl-4-(1H-2-pyridon-1-yl)-6-cyano-2H- chromene with mp 146-148 C and 2,2-dimethyl-4-(1H-2-pyridon- 1-yl)-6-cyanochroman-3-ol with mp 244 °C. There follows, starting with the words "by analogy one obtains", a long list of chemical names, some with indications of melting point. Among them are the following:

2,2-dimethyl-4-(1H-3-hydroxy-2-pyridon-1-yl)-6-cyanochroman-3- ol, mp 262-265 °C (page 9, line 1, of the published application),

2,2-dimethyl-4-(1H-3-hydroxy-2-pyridon-1-yl)-6-cyano-2H- chromene, mp 290-295 °C (page 9, line 2, of the published application),

2,2-dimethyl-4-(1H-4-hydroxy-2-pyridon-1-yl)-6-cyanochroman-3- ol, mp 248-250 °C (page 9, line 3, of the published application),

2,2-dimethyl-4-(1H-5-hydroxy-2-pyridon-1-yl)-6-cyanochroman-3- ol, mp 256.5-258 °C (page 9, line 5, of the published application),

2,2-dimethyl-4-(1H-3-hydroxy-6-pyridazinon-1-yl)-6- cyanochroman-3-ol, mp 254-256 °C (page 11, line 40, of the published application) and

2,2-dimethyl-4-(1H-4-hydroxy-6-pyrimidinon-1-yl)-6- cyanochroman-3-ol, mp 235-237 °C (page 11, line 50, of the published application).

The board shares the appellant's view that the skilled person infers from this information the instruction to react the starting materials covered by the above names under the conditions indicated in the example, and then isolate the product with the given melting point from the reaction mixture by chromatographic separation. The board is satisfied that the products thus defined by starting materials, reaction conditions, isolation conditions, melting point and a name which, though general, is correct, are clearly identical to the above-mentioned (incorrectly designated) products originally disclosed. Therefore, claims 11 to 16 likewise do not infringe Article 123(2) EPC.

5.6 The application therefore has to be remitted to the first instance for resumption of the examination proceedings on the basis of the claims according to the auxiliary request. At the same time, claim 8 must also be examined for compatibility with Article 52(4) EPC.


For these reasons it is decided that:

The decision under appeal is set aside. The case is remitted to the first instance for resumption of the examination proceedings on the basis of the claims according to the auxiliary request.

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