T 0181/82 (Spiro compounds) of 28.2.1984

Summary of Facts and Submissions

I. European patent application No. 80 810 093.7 filed on 21 March 1980 and published on 15 October 1980 with publication No. 0 017 617 claiming the priority of the Swiss prior application of 27 March 1979 was refused by decision of the Examining Division of the European Patent Office dated 8 July 1982 on the basis of the nine claims filed on 23 February 1982. Claim 1 is worded as follows:

"1. Compounds of the formula

(FORMULA I)

and their acid addition salts, in which n is a whole number from 1 to 4, R1 is hydrogen or CH3, R2 and R3 mean, independently of one another, hydrogen, C1-C18, alkyl, unsubstituted C6-C10 aryl or C7-C9 aralkyl or alternatively chlorine or C1-C4 alkyl substituted C6-C10 aryl or C7-C9 aralkyl or else R2 and R3 together with the C atom to which they are bound form a cycloalkane or alkyl cycloalkane residue with 5-20 C atoms or a polyalkyl piperidine residue, R4 represents, if n=1, C3-C8 alkenyl, C3-C5 alkinyl, unsubstituted or C1-C4 alkyl substituted C7-C9 aralyl or a -CH2-CH(R5)-OR6 residue, in which R5 is H, CH3, C2H5 or phenyl and R6 means hydrogen or the residue of an aliphatic, cycloaliphatic or aromatic monocarboxylic acid with up to 18 C atoms, and, if n=2, represents 1,4-butene-2-yelene, m- or p-xylylene or a residue of the formula -CH2-CH(R5)-O-R7-O-CH(R5)-CH2-, in which R5 has the meaning given above and R7 means the divalent residue of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid with 3-14 C atoms, and, if n=3, represents a residue of the formula (FORMULA II) in which R5 has the meaning given above and R8 means the trivalent residue of an aliphatic or aromatic tricarboxylic acid with 4-18 C atoms, and, if n=4 represents a residue of the formula (FORMULA III) in which R5 has the meaning given above and R9 means the tetravalent residue of an aliphatic or aromatic tetracarboxylic acid with 6-20 C atoms."

II. The application was refused on the grounds of lack of inventive step. The most comparable state of the art was represented by DE-A-2 606 026 (=A document), in which UV stabilisers very similar in structure to the subject-matter of the application were already described. The applicant did indeed demonstrate the increased resistance to extraction of a compound according to the application by adducing a comparative test; but he failed to note that the comparative test needed to be carried out with the structurally most comparable N-propyl or N-butyl compound disclosed in (a). Although these compounds were not described by means of an example of their preparation, Process Claim 9 together with the list on pages 8-10 of the description taught specifically about the preparation at least of butyl compounds. The question of which state of the art should be used for comparative tests could not be seen in isolation from the technical problem, the solution to which needed to be examined as to inventive step. The problem in the present case was to improve known compounds according to (a) in respect of their resistance to extraction. However, it was one of the basic facts known to chemists that the lipophilic properties of a molecule were enhanced by introducing hydrocarbon groups. This automatically reduced the degree of extractability by water from a lipophilic environment (polypropylene). To that extent the comparative test submitted by the applicant provided no more than further proof of a fact with which the person skilled in the art was familiar. Moreover there was no evidence as to why the properties found in the allyl compound should also be attributed to the benzyl or hydroxyethyl compound. The latter residue was generally regarded as hydrophilic and should therefore tend rather to facilitate extractability with water. With regard to the claimed compounds with n>1 it was still necessary to say why the reduction in extractability by water by multiplying the molecular size should not have been obvious, particularly as the relevant state of the art had already provided some ideas on this (cf., for example, DE-A-2 500 314 (=B document). Finally, the definition R4=C3-8 alkenyl and C3-5 alkinyl in Claim 1 covered compounds whose existence was doubtful and which therefore were not adequately disclosed (Article 83). The question of whether this ought to entail a clarification of the wording of the claim (Article 84 EPC) could be left open.

III. An appeal was lodged against this decision on 25 August 1982 with payment of the prescribed fee, the Statement of the Grounds submitted on 19 November 1982 being roughly along the following lines: it could not be admissible to prescribe to the applicant as a comparative substance a compound not already specifically described in the state of the art. Moreover (a) did not indicate how piperidine spiro-oxazolidiones could be modified without losing their light-protection effect or that a technically useful effect (resistance to extraction) not considered at all in the document also occured. At any rate, (a) did not suggest any reason for manufacturing the claimed compounds. The test had shown that no obvious facts with regard to the N-allyl compound according to the application could be inferred from the known NH compound. If it were impossible to predict the effect of the N substitution for the N-allyl compound, it would be equally impossible for an N-aralkyl, N-hydroxyalkyl or other R4 compound. With regard to the doubt as to the existence and manufacturability of the alkenyl or alkinyl compounds, the application was addressed to the person skilled in the art; however, the latter was perfectly aware that the only residues meant were those in which the C atom bound to the nitrogen was primary.

IV. The Board pointed out that it would appear possible to revoke the contested decision if a comparative test were adduced in order to show that the intended improvement on the objectively, i.e. structurally, most obvious state of the art unexpectedly succeeded. The compound chosen so far by the appellant was not suited to this because the state of the art could be regarded as also including compounds N-methylated in the 3-position, which are structurally nearer to the subject-matter of the application and result from the conversion of the starting substances according to Claims 3 to 7 in (a) with methyl bromide (=C1 alkyl bromide) according to Claim 9 and which belonged to the state of the art as stated in the decision on "Diastereomers" (Official Journal of the EPO 1982, 296). Moreover it was not possible to claim compounds which were known to be unsuitable for solving the problem (R4=C3-C8 alkenyl and C3-C5 alkinyl).

V. The appellant disagreed with the Board and requested oral proceedings, which took place on 14 February 1984. In the course of the proceedings the appellant stressed that the terms C1, alkyl and C4 alkyl in Claim 9 of citation (a) were a means of defining a range and did not serve to individualise the specific representatives of these limits of the range. Otherwise, all the intermediate elements in the range would also have to be regarded as individualised. But this could not be the case. The characteristic feature of a range was that it permitted selective inventions over the whole range. The C1 alkyl bromide was not therefore described as being differentiated, but represented only the initial element in the range of groups indicated, which contained a further seven alkyl bromides. Consequently, the definition given in Claim 9 in (a) represented a list of eight starting substances of which none was emphasised in particular. The question of whether the initial and terminal elements in a range were individualised could not depend upon the way in which it was defined, especially as there were known to be several possible definitions containing identical technical information. The other starting substances required in order to produce the N8-alkylated end products by the process described in Claim 9 were listed in Claims 3 to 7 and still represented a list of 30 possible starting substances. Each end product was thus the result of two variable parameters. This meant that preparing the end products required two classes of starting substances, one containing at least 30 and the other eight possible starting substances. As the Board's decision conceded (T 12/81, Official Journal of the EPO 1982, 296), a substance produced by the conversion of a special pair from two classes of starting substances represented a choice under patent law and was therefore new. A comparison with a new compound which itself again represented a choice and therefore a potentially patentable invention could not be required. It was indeniable, moreover, that according to (a), compounds in which R5 is hydrogen are chosen by preference. So if, as suggested in another decision of the Board (T 24/81), Official Journal of the EPO 1983, 133), all the embodiments published in the only relevant document from the state of the art were taken into consideration, the skilled person would be prompted to choose for this structural group only a compound in which R5 means hydrogen. But it would not be possible to say that, if all the embodiments were examined objectively, (a) prompted the choice of a compound in which R5 was C1 to C4 alkyl. Finally, attention was also drawn in this connection to another decision of the Board (T 01/80, Official Journal of the EPO 1981, 206). According to this decision, a document did not furnish any inducement to employ a special class of compounds if the latter was merely mentioned incidentally and not emphasised by an example. The inventive step had therefore to be judged in the light of what the skilled person adopted from the state of the art as being particularly suitable for solving a specific problem. When trying to improve the known light stabilisers he would certainly have chosen a compound with R5 = Hydrogen and not one with R5=alkyl. It had also been demonstrated that a derivative according to the application in which R5 was allyl was an unexpectedly better light stabiliser than the N-unsubstituted product which had become prominent in the state of the art. The appellant requests that the contested decision be revoked and that a patent be granted on the basis of Claim 1 worded as follows: "Compounds of the formula (FORMULA I) and their acid addition salts, in which n is a whole number from 1 to 4, R1 is hydrogen or CH3, R2 and R3 mean, independently of one another, hydrogen, C1-C18 alkyl, unsubstituted C6-C10 aryl or C7-C9 aralkyl or alternatively chlorine or C1-C4 alkyl substituted C6-C10 aryl or C7-C9 aralkyl, or else R2 and R3 together with the C atom to which they are bound form a cycloalkane or alkyl cycloalkane residue with 5-20 C atoms or a polyalkyl piperidine residue, R4 represents, if n=1, allyl, methallyl, unsubstituted or C1-C4 alkyl substituted C7-C9 aralkyl or a -CH2-CH(R5)-OR6 residue, in which R5 is H, CH3, C2H5 or phenyl and R6 means hydrogen or the residue of an aliphatic, cycloaliphatic or aromatic monocarboxylic acid with up to 18 C atoms, and, if n=2, represents 1,4-butene-2-ylene, m- or p-xylyl or a residue of the formula -CH2-CH(R5)-O-R7-O-CH(R5)-CH2- in which R5 has the meaning given above and R7 means the divalent residue of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid with 3-14 C atoms, and, if n=3, represents (FORMULA II) in which R5 has the meaning given above an R8 means the trivalent residue of an aliphatic or aromatic tricarboxylic acid with 4-18 C atoms, and, if n=4, represents a residue of the formula (FORMULA III) in which R5 has the meaning given above and R9 means the tetravalent residue of an aliphatic or aromatic tetracarboxylic acid with 6-20 C atoms." The appellant does not consider it necessary to carry out the comparative test suggested by the Board (see IV above). It is requested in the alternative that the following questions be put to the Enlarged Board of Appeal: (a) Given the prior description of a process for preparing a group of compounds which is designated merely by the fact that a group of compounds consisting of starting substances is converted with a group of compounds consisting of reactants, is a specific individual representative of the synthesizable group anticipated in a manner prejudicial to novelty or only the resulting group of compounds as a generic concept or range? (b) Does the mere description of a range, which must necessarily be defined by its limits, represent a disclosure of (even only) one individual element in this range?

Reasons for the Decision

1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is, therefore, admissible.

2. It is beyond question that citation (a) referred to in the preamble to the description represents the closest prior art to the subject-matter of the application. In that document, specific light stabilisers with the skeleton of 1-oxa-3,8-diaza-spiro(4,5)-decane are already described for polymers (cf. Claims 1 and 11-14), preference being given to those tetramethylated in the 7 and 9 positions and alkylated in the 2 position by the residues designated more closely in Claims 3-7. The conversion of these preferred derivatives with C1-C4 alkyl bromide to the corresponding 8-alkyl compounds is also described (cf. Claim 9 and the claim on which it depends). With regard to the nomenclature of the spiro compounds which are of interest here, it must be noted that when the transition is made from spiro to dispiro compounds (comparative compound according to the application) the numbering of the heterocyclic skeleton and thus the numbering at the nitrogen atom, which is important in this context, changes from 8 to 3. For greater clarity, however, both classes of compounds whose piperidine nitrogen atom is replaced by 8-substituted spiro compounds will be defined below. According to the description relating to the present application, such substances have an excessive volatility and tendency to migration (cf. page 1). Given the considerable structural similarity between the known compounds and those being claimed, it is not necessarily plausible nor has it been made plausible that these disadvantages are overcome by the compounds according to the application. Advantages to which the applicant refers by way of comparison with the closest prior art, but which are not adequately verified, cannot be considered when it comes to determining the problem of the invention. Nor therefore can they be taken into account when the inventive step is assessed (cf. T 20/81 "Shell/aryloxybenzaldehydes", Official Journal of the EPO, 1982, 217).

3. According to the comparative test submitted on 24 September 1981, the improvement achieved according to the application apparently consists in increased resistance to extraction on the part of the light stabilisers in respect of water (at 90°C). In that test , compound No. 31 from Table 1 in (a) was compared with the corresponding 8-allyl derivative according to the application and a threefold increase in the extraction time to a 50% residual content was achieved. In submitting this report on the test the applicant wanted to take account of the fact that in the present case the state of the art approaches the subject-matter of the application so closely that it is necessary to submit an indication of inventive step which is often used in chemistry and frequently carries conviction, i.e. evidence of superior properties.

4. The appellant holds the view that an unexpected effect vis-à-vis a preferred representative of the state of the art is sufficient. Additional evidence in respect of a representative which was mentioned only in passing and had come to light only subsequently when the present application became known was not necessary in order to make an inventive step plausible. On the other hand it has to be pointed out first of all that a comparison by its very nature requires familiarity with the subject-matter of the application; otherwise there can be no possibility either of determining the relevant state of the art or of assessing the invention with regard to novelty and inventive step. Familiarity with the invention is therefore a prerequisite for ascertaining the disparity between it and the state of the art. Examination with regard to inventive step is limited to the question of obviousness in the overall light of the state of the art and from the viewpoint of the closest citation (looking forward) and not from that of the invention (looking backward). If the appellant regards only the preferred compounds from a citation as comparable, he is concentrating on the technical progress compared with the known substances considered most effective. Technical progress is not a requirement for a patent under the European Patent Convention. However, an effect demonstrated by means of a comparative test can be regarded as an indication of inventive step; the only tests suitable for this are those which are concerned with the structural closeness to the invention, because it is only here that the factor of unexpectedness is to be sought.

5. To be relevant, such comparative tests must meet certain criteria. These include the choice of a compound disclosed in the application and of a comparative substance taken from the state of the art; at the same time, the pair being compared should possess maximum similarity with regard to structure and application. The compound chosen in the comparative test in accordance with the application, namely 3-allyl-2,2,4,4-tetramethyl-7-oxa-3,20-diaza- 21-oxo-dispiro-(5,1,11,2)-heneicosane, can presumably be regarded as disclosed because it appears to be identical with the reaction product not designated more closely in Example 1 (compare its melting point with that of the corresponding 20-allyl compound according to Example 4). The 2,2,4,4-tetramethyl-7-oxa- 3,20-diaza-21-oxo-dispiro-(5,1,11,2)-heneicosane was chose as the comparative compound according to the state of the art. Although this compound is described in (a) (cf. the original page 5, lines 1/2), it does not represent the structurally closest prior art. The requirement for a comparison with the closest prior art is based on the principle of the structural dependence of the properties of chemical substances i.e. on the fact that these properties reflect the structure of the substances. Given the similar properties to be expected in view of the structural similarity of two substances, evidence of an abrupt improvement can be regarded as unexpected. The greater the structural difference between the compounds being compared, the less unexpected are any differences in their effects. So if a meaningful statement is to be made in order to render an inventive step plausible, compounds having a maximum structural resemblance must be compared with one another.

6. This is not the case with the comparative test submitted because an 8-methyl spiro compound is structurally closer to an 8-allyl spiro compound according to the application than a spiro derivative which is unsubstituted in this position (compound No. 31 from (a)). The Board proposed a basis for comparison any 8-methyl derivative of the spiro compounds specified in Claims 3-7 from (a). The appellant failed to go along with this because he does not regard these substances as the subject-matter of a prior description.

7. In its Decision T 12/81 "Diastereomers" (Official Journal of the EPO 1982, 296), the Board expressed the view that a chemical substance not explicitly described in a prior application but nevertheless (implicitly) described by indication of the starting compound and the process specified in connection therewith belongs to the state of the art. In Claims 3-7 in (a), the reference to Claim 2, which lays down the variables R1 and R2 as methyl groups, R5 as hydrogen and m as zero, indicates that quite specific spiro compounds unsubstituted in the 8 position are individual compounds which according to Claim 9 are to be alkylated in this position with a C1-C4 alkyl bromide (cf. the reference to Claims 1-7 in Claim 9). Here, C1 alkyl bromide is a synonym of methyl bromide. According to the principle laid down in the decision on "Diastereomers", whereby a process described specifically by reference to the starting substances and working method includes in the material disclosed in this teaching the product which inevitably results therefrom, the 8-methyl derivatives of the spiro compounds according to Claims 3-7 belong to the state of the art. If the appellant believes that designating the above-mentioned range is simply and solely a means of defining it, he fails to recognise the material disclosed in the teaching according to Claim 9, whereby, over and above the range of groups, the methyl bromide singled out by designation represents a means of alkylation for the above-mentioned spiro compounds. This information, which the person skilled in the art can unquestionably put to practical effect, places the designated 8-methyl spiro compounds within the state of the art, irrespective of whether they have been manufactured. For the Board a designated compound is anticipated state of the art, whatever its purpose may be.

8. The appellant stated further that the range of "C1-C4 alkyl bromides" could also be defined differently, for example as "alkyl bromides with a maximum of 4 C atoms", "alkyl bromides with fewer than 5 C atoms", or "alkyl bromides with more than 0 and fewer htan 5C atoms". Despite the different formulation, such ranges had an identical information content and were understood by the skilled person as a disclosure of all 8 possible alkyl bromides without their being individualised. It cannot be denied the the eight conceivable alkyl bromides are covered by all these definitions; a strict distinction must be drawn between this purely intellectual content of the definitions and their information content in the sense of a specific teaching with regard to technical action. While the "C1-C4" definition specifically designates methyl bromide as an individual compound and the butyl bromides as a family (4 possibilities), the "maximum C4" definition does not individualise methyl bromide because this substance is not designated or otherwise more closely described. The other two definitions skilfully avoid any specific statement about methyl bromide or indeed about the C4 family. When the teaching from a citation is interpreted, special attention must be paid to the material actually disclosed in the sense of a complete, specific technical rule. A group of compounds in which the substituent is characterised by a range teaches the skilled person only about the individuals specifically designated from the group. The formulation C1-C4 alkyl bromide in Process Claim 9, which is chosen in citation (a), therefore describes the corresponding 8-methyl derivatives in every detail in connection with the spiro derivatives according to Claims 3-7 envisaged therefor.

9. This interpretation of the disclosure according to (a) also leaves no further scope for the appellant's additional objection to the effect that the listing of the spiro compounds unsubstituted in the 8 position on the one hand and the eight alkyl bromides on the other results in an abundance of possible combinations which had to be regarded without exception as not described in a prior document. The appellant cannot cite the principle of the novelty of such combinations from two lists of different starting substances, which the Board explicitly approved in its decision on "Diastereomers". As stated, this is not what the present case is about for the precise reason that Claim 9 cannot be regarded as a list of all the eight alkyl bromides which it covers.

10. In view of the above it is not hard to see why the Board considered as inappropriate the comparative tests based on an 8-propyl and 8-butyl spiro compound, which the first instance had demanded, and suggested comparative tests with an 8-methyl spiro compound.

11. As stated, a relevant comparative test is not available, so the technical problem with which the present application is concerned must be considered to be the proposal of further light stabilisers for polymers. This problem is solved by the provision of the polyalkyl piperidine-spiro-oxazolones defined more closely in Claim 1.

12. This teaching has not already been described in the prior art available to the Board and is thus new. It is therefore necessary to examine whether it is based on an inventive step. For this purpose, reference must be made to citation (a), in which light stabilisers for polymers with the same skeleton are already described. It also already mentions 8-alkyl derivatives with 1-4C atoms in the alkyl residue. The claimed compounds differ therefrom solely in the 8 position in as much as they contain, amongst other things, the two alkenyl residues allyl and methallyl. It is therefore necessary to examine whether the replacement of the known C1-C4 alkyl residues by the alkenyl residues according to the application was obvious in view of the technical problem of proposing further light stabilisers. The original pages 24 and 25 of (a) contain a description of the stabilisation of polypropylene against UV radiation by the addition of seven different polyalkyl piperidine-spiro-oxazolone derivatives and the statement that all the compounds pass the test equally well (reduction of breaking elongation to 10% after more than 800 hours). The first six of these compounds are derived from 7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro-(4,5)-decane and represent its 2-butyl, 2-iso-pentyl, 2-undecyl, 2-methyl-2-propyl, 2-methyl-2-nonyl and 2,2-dibenzyl derivatives; the seventh compound is a dispiro derivative (correct bracket designation (5,1,5,2)). The skilled person infers from this that the stabilising effect is accounted for essentially by the skeleton of piperidine-spiro-oxazolone, which is common to these compounds, and not by its special substitution. In view of this teaching it was obvious, given the present problem of proposing further light stabilisers, to provide spiro compounds with the same skeleton and similar substitution in the 8 position as well. The 8-allyl and 8-methallyl derivatives according to the application are such compounds with similar substitution because they differ from the known alkyl derivatives only in the degree of saturation, i.e. the absence of two hydrogen atoms.

13. The appellant, on the other hand, takes the view that only the spiro compounds unsubstituted in the 8 position were obvious because only they were emphasised as preferred compounds. He also refers in this connection to the Board's decision in T 01/81 "Carbonless copying paper" (Official Journal of the EPO 1981, 206), whereby a document has not furnished any inducement to employ a special class of compounds for the production of improved copying papers because this special class of compounds was merely mentioned incidentally and not emphasised by an example. This passage, which is quoted out of context, in no way confirms this view, which takes no account of two essential differences between the two cases compared. In the decision referred to, it is stated that "the mere mention of a group of substances amongst numerous other groups of substances permits at best a surmise of comparable suitability and effectiveness for the purpose in hand if these groups of substances are interchanged". In other words, any such mention of a class of substances indicates that only comparable, but not improved, effectiveness can be expected. As stated in section 11, the problem according to the application does not consist in improving known stabilisers but in proposing further stabilisers of comparable effectiveness; consequently, the 8-alkyl spiro compounds mentioned in (a), but not specially emphasised, were indeed able to provide a stimulus only for their structural development. Moreover, the further prerequisite consisting in the mere mention of one alongside numerous other groups of substances is not fulfilled because (a) describes only a single class of substances, namely that of polyalkylpiperidine-spiro-oxazolones. In the later decision on "Metal refining", T 24/81 (Official Journal of the EPO 1983, 133), the Board furthermore expressed the opinion that, when an examination as to inventive step is being carried out, all those previously published embodiments must be taken into consideration which offered a suggestion to the skilled practitioner for solving the problem addressed, irrespective of whether they are particularly emphasised in the citation.

14. With regard to the alternative request, Article 112(1) EPC provides for the Enlarged Board of Appeal to have any question referred to it only in connection with important points of law. Such points of law do not arise in this instance. The two questions formulated by the appellant are concerned with whether the person skilled in the art can understand the technical content of citation (a) without hesitation on the strength of his own knowledge; but this is primarily a technical question because it requires the skilled person to interpret technical information.

ORDER

For these reasons, it is decided that:

1. The appeal is dismissed.

2. The request for the case to be remitted to the Enlarged Board of Appeal is refused.