Wette r w u r d e n die i so typen St- u n d Ba -Verb indungen un te r - s u c h t sowie alIgemein die M6gl ichkei ten ff~r Synthese , Ionen- subs t i t u t i on , Glasb i ldung u n d Is Die ers ten Ergebnisse seieli kurz z u s a m m e n g e f a B t (aus- ffihrliche Pub l i ka t i on in Vorbere i tung) : Zun~chs t w u r d e n CaCu [Si4010], SrCu [Si4010 ] und BaCu [Si~Ox0 ~ ohne Flul3mittel- zusa tz d u t c h Fes tk6 rpe r reak t ion (PreBtablet ten) aus fe inst - g e m a h l e n e m Erda lka l i ca rbona t , CuO u n d Q u a r z m e h l her- gestellt . Die R e a k t i o n war erst nach Erhitzel i au f 1000 ~ (100 Std) und lanngsamem Abkfihlen auf 800 ~ vol ls t~ndig. Eine Erh6hu l lg des CaO- oder CuO-Geha l tes bet der Syn these des Agypt isc t l Blau h a t t e ke inen pos i t iven Effekt . Dagegen erwies sich der Zusa tz voli Borax , NaNO3, Na2CO 3 u n d beson- ders voli Li2CO 3 (jeweils 0,t bis 0,3 Mol auf I Mol CaCu[Si4Ox0]) als auBerordent l ich wi rksam. II1 alien F~llen b i lde ten sich nach Erh i t zen auf 850- -900 ~ l euch tend b laue P roduk te , deren R S n t g e n d i a g r a m m e d e m des CaCu[Si4010 ] en t sp rachen . Die 1Reaktion ohne F luBmi t t e l zusa t z wird begf ins t ig t und zu n iedr igeren T e m p e r a t u r e n ve r schoben (900--950 ~ wenn m a n Calcit du rch Gips oder Ca(OH)~ ersetzt , CuO durch Malachi t u n d Q u a r z m e h l du rch Kieselgel. Bet Zusa tz gr6Berer Mengen yon Borax , Soda oder Na2Si2Q-Glas (jeweils 1 - -4 Mol auf t Mol CaCu [SilO10]) en ts tehel i nach Erh i t zen auf t t 50 bis 1300 ~ h o m o g e n e b laue Gl~ser, aus deneli n a c h W~rmebe - h a n d l u n g e n aber ke in s Blali, sondern T r i d y m i t u n d Ca-Sil icate kristal l is ieren. Auch diese teilweise noch glasigen P r o d u k t e s ind in t ens iv blau. F~r die Zt~chtung yon Einkris t~l l - chen (quadra t i sche P l~ t t ehen m i t Kan ten lXngen bis ca. t m m ) waren Zus~Ltze voli Borax, Na2SO~ oder P b O gfinstig. Gem~B t h e r m o a n a l y t i s c h e n U n t e r s u c h u n g e n m i t e inem Met t - l e r -Thermoana lyze r u n d m i t He iz rSn tgen ist die t h e r m i s c h e Stabi l i t~t des ~ g y p t i s c h Blau u n d der entspr . Sr- u n d Ba-Ver- b i n d u n g wesent l ich hSher als b isher angenommel i . Dabe i w u r d e n die re inen, f lui3mittelfreien Verbindungenn in s t r 6 m e n d e r Lu f t (5 l/h) m i t 2 ~ auf 1230 ~ aufgehe iz t u n d abgeki]hlt . Es zeigte sich in allen drei Fiillen, dab der A b b a u Cue+-->Cu x+ v o m e i l igebauten Erda lka l i - Ion abhS, n g t u n d he l m Abki ih len wieder vollstXndige R e o x y d a t i o n s t a t t f i nde t , dab aber n u r BaCu[Si~O10 ] vollstiilidig reversibel wieder a u f g e b a u t wird.

E ingegangen a m 3 . F e b r u a r t975

I. Mazzi, F., Pa bs t , A.: Amer . Min. 47, 409 (1962) 2. Noll, W., Ho lm, R., Born, L.: N. Jb. Miner. Abh. 122, 119

(1974) 3. Chase, W. T., in: Science and Archaeology, p. 80 (ed. R. H.

Brill). Cambridge , Mass . : M I T Press 1971

plexes which by themse lves exhibi t no absorpt ion . For example , in t he presence of Mn 2+ (0.05 to 0.20 M) the absorp t ion of the Cu2+-Tt-IT s y s t e m will be less t h a n in a Mn2+-free sy s t em , and f rom th i s decrease in abso rp t ion one can obvious ly calculate t he s tab i l i ty c o n s t a n t of the Mn2+-THIT 1:1 complex : log

Mn KMn (THT) = - - 0.3 t == 0. t I [4]. Similarly, in t he presence of Ag + (5 • t0 -a to 8 • 10-3 M) one ob ta ins for the A g + - T H T t :1 complex : l og / fAg (TilT) = 3.51 • 0 . t4 [4]. The o u t s t a n d i n g a d v a n t a g e of th i s me thod , which m a y also be used for o ther th ioe the r complexes , is t h a t smal l differences in absorp t ion can be m e a s u r e d ve ry exact ly , so t h a t it is possible to de te rmine t he s t ab i l i ty of ve ry weak complexes like Mn (THtT) 2+ as well as of r a the r s table species like Ag(THT)+. Here it should be men t ioned t h a t t he s tab i l i ty of t he la t t e r species is close to t he one measu red in aqueous solut ion b y W i d m e r and Schwarzenbach [6] wi th the si lver electrode for the Ag+-2 ,2 ' - th iodie thanol I :1 complex (log Ag HAg L = 3.60 ; I = t .0, KNOa; 20 ~ To conclude, t h o u g h no t ve ry s table, the complexes fo rmed be tween T H T and Mn 2+ or Cu 2+ are still s table enough to create specific s t ruc tu re s [3]. Moreover, these me ta l ion- th ioe the r in te rac t ions are weak enough to allow r eady rear ran- g e m e n t of complexes as necessa ry in ca ta ly t ic processes. W e are now ex t end ing our s tudies to o ther me t a l ions an d o ther th ioe the r l igands wi th the object of ga in ing an overview of the s t ab i l i ty of t hese complexes .

The suppo r t of th is research by the Swiss Na t iona l F o u n d a t i o n is gra tefu l ly acknowledged.

Rece ived F e b r u a r y 24, 1975

1. McCormick, D. B., Griesser, R., Sigel, H. , in: Metal Ions in Biological Sys tems , Vol. 1, p. 2 t3 (ed. H. Sigel). New York: Dekke r 1974

2. Nakon , R., Beadle, E. M., Jr. , Angelici , R . J . : J. Am. Chem. Soc. 96, 719 (1974)

3. Sigel, H. , etal.: Biochemis t ry 8, 2687 (t969); Griesser, R., etal.: ibid. 12, t917 (1973)

4. The range of error g iven cor responds to twice the s t a n d a r d deviat ion.

5. Behest , H. A., H i ldebrand , J . A . : J. Am. Chem. Soc. 71, 2703 (1949)

6. Widmer , M., Schwarzenbach , G.: Chimia (Aarau) 24, 447 (1970); \ u M.: Disse r t a t ion Nr. 4868, ETt-I Zfirich (t972)

Stability of Metal Ion-Thioether Complexes

V. M. Rhe inbe rge r and H. Sigel

I n s t i t u t e of Ino rgan ic Chemis t ry , Un i ve r s i t y of Basel, Basel , Swi tzer land

Th ioe the r moie t ies are po ten t i a l b ind ing si tes for me ta l ions in p ro te ins and enzymes , due to t he n a t u r a l occurrence of comp- ounds like L-meth ion ine and d-b io t in [t ]. However , so far t he in te rac t ions be tween s imple th ioe thers and biologically impor- t a n t m e t a l ions, like Mn 2+, Cu 2+ and Zn 2+, have ha rd ly been inves t iga t ed a t all. There are two reasons for th i s : (i) such complexes are ve ry weak, and (ii) p H - m e t r i c de t e rmina t i ons of s t ab i l i ty c o n s t a n t s are no t possible. As a consequence only th ioe the r complexes w i t h po l yden t a t e l igands con ta in ing add i t iona l b ind ing sites, like a m i n o or ca rboxy la te groups, h a v e been s tud ied [1, 2]. W e now repor t on the s t ab i l i ty of t he complexes fo rmed be tween Mn 2+, Cu 2+ or Ag + and t e t r a h y d r o - th iophene , t he th ioe the r m o i e t y of d-biot in (v i t amin H), k n o w n f rom p m r s tud ies to in t e rac t w i th me t a l ions [3]. The coord ina t ion of Cu 2+ to t e t r a h y d r o t h i o p h e n e (TILT) exhib i t s absorp t ion 'a t 359 n m (e = 93 • 9 M -1" c m-l ) [4]. W i t h the aid of difference spec t ra and increas ing a m o u n t s of Cu(C10~)2 (0.02 to 0.30 M ; T I l T = 5 • t0 -3 M; 50% aqueous e t h a n o l ; / = 1.0, NaCIO~; 25 ~ it is possible to de t e rmine t he s tab i l i ty c o n s t a n t of t he Cu2+-THT 1 : 1 complex b y t he m e t h o d

Cu of Behes t and H i l deb rand [5] : log KCu(THT ) = 0.02 =E 0.04 [4]. This is, of course, a ve ry uns t ab l e complex b u t it h a s the advan - t age t h a t me ta l ions like Mn 2+ can compe te for t he coord ina t ion a t T H T in a s y s t e m t h a t con ta ins b o t h Cu 2+ and Mn 2+. Th i s allows one to de t e rmine t he s tab i l i ty of me t a l i o n - T H T corn-

Zur elektronenmikroskopischen Darstel lung von Lignin-Kohlenhydrat-Komplexen

D. Feligel

Ins t i t l i t ft~r Ho lz fo r sehung der Universit~Lt Miinehen

Bei der U n t e r s u c h u n g nicht-cel lu los ischer Po lysacchar ide (Polyosen) aus I-Iolz wurde m e h r f a e h festgestel l t , dab zu- m i n d e s t ein Tell d a v o n n ich t yon L ign in res ten zu t r e n n e n is t [t] . Es wird dahe r auf eine chemische Bindul ig zwischen Po lyosen u n d L ign in geschlossen, u n t e r Bildul ig yon Lign in- K o h l e n h y d r a t - K o m p l e x e n (LIKIK). Solche Komplexe , die sieh in der P o l y s a c c h a r i d - Z u s a m m e n s e t z u n g ulld dem Lign in- ante i l un te r sche iden , werden s u c h in F r a k t i o n e n gefnnden , die alis der T r e n n u n g des Alka l i -Ex t rak te s (5%ige KOH) yon Fichten-Holocel lu lose an Io l i enaus t ausche r s t a m m e n [2]. Bet der e l ek t ronenmikroskop i schen U n t e r s u c h u n g der Frak- t ionen werden durch N e g a t i v k o n t r a s t i e r u n g m i t U r a n y l a c e t a t fibrillgre S t r u k t u r e n s ichtbar . I n einer Frakt iol i , in der der Po lysaechar id -Ante i l vorwiegend aus G a l a e t o g l u c o m a n n a n bes teh t , h a b e n die Fibrilleli D u r c h m e s s e r yon IO- -20 /~ . I n den ande ren F rak t ionen , bet denen me i s t Arab inoxyla l l im Po lyosenan te i l t iberwiegt, be t rgg t der F ib r i l l en -Durehmesse r 50- -80 A. Diese dickeren Fibri l len zeigen e inen un te r seh ied- l ichen K n g u e l u n g s g r a d , der of fenbar v o m L ign inan te i l ab- h g n g t [3]. K o n t r a s t i e r u n g s v e r s u e h e an e inem Lig l i inprgpara t (~ thanol l ignin) e rgaben eilie posi t ive A n f g r b u n g m i t Ura- ny lace ta t . D a m i t war eine Ui i t e r sche idung zwisehen Un te r - g rund u n d eventue l l ange l age r t em Lign in bet den Polyosen- fibril len z l ingehs t n i ch t m6glich. Es w u r d e n daher bet P roben der F r a k t i o n e n drei versch iedene K o n t r a s t i e r u n g s m e t h o d e n angewende t : 1. B e h a n d l u n g m i t Urany l aee t a t , 2. K e g e l b e s c h a t t u n g m i t Plat in-IKohle (s imut-

182 N a t u r w i s s e n s c h a f t e n 62 (t975) �9 by Spr inger-Ver lag 1975

o.

Fig. l a u. b. Lignin-Kohlenhydrat-Komplex mit hohem Li- gninanteil (78%). (a) Kontrastierung mit Uranylacetat, (b) Simultanbeschattung mit Platin-Koble

tan), 3. Uranylacetat-Behandlung mit anschlieBender Pt-C- Beschattung. Die mit Uranylacetat behandelten Proben zeigen deutlich die fibrill/ire Struktur der Polyoseu (Fig. I a). Diese Fibrillen sind auch bet beschatteten Proben mit geringem Ligninanteil zu erkennen. Dagegen sind bet beschatteten Proben mit hohem Ligninanteil die Iibrill~ren Strukturen verdeckt, da die Platin-Kohleschicht den Gesamtkomplex umhflllt (Fig. t b). ~rbergangsformen finder man bet der kombi- nierten Kontrastierung. Dadurch ist einerseits gesichert, dab bet Uranylacetat-behandelten und bet beschatteten PrS~- paraten jeweils sich entsprechende Teilchen beobachtet wer- den, andererseits k6nnen danach die sehr dunklen 13ereiche um die Polyosenfibrillen und -fibrillenkn~uel bet Uranyl- acetat-behandelten Proben dem Lignin zugeordnet werden. Aus den 13eobachtungen ergibt sich, dal3 Lignin offenbar an die Oberfl~iche der Polyosenfibrillen gebunden ist und solche Fibrillen daher schon primer in der Zellwand vorhanden sein mfissen. Eine ausfiihrliche Darstellung folgt in der Zeitschrift ,,Holz- forschung".

Mit Unterstfltzung der Deutschen Forschungsgemeinschaft.

Eingegangen am 12. Februar 1975

t. Kringstad, IK.P., Cheng, C.W.: Tappi 52, 2382 (1969) Smelstorius, J .A.: Holzforschung 28, 99 (1974) u.a.

2. Fenget, D., Przyklenk, M.: Svensk Papperstidn. 78, 17 (t975)

3. Fengel, D.: ibid. (ira Druck)

A N e w T r i t e r p e n o i d f r o m the R o o t s of Glycyr rh i za g labra L.

C o n s t i t u e n t s of Loca l P l a n t s X X I

M. H. A. Elgamal and M. 13. E. Fayez

National Research Centre, Dokki-Cairo, Egypt

In addition to the known El, 2] minor oleanane triterpenoids of liquorice (Glycyrrhiza glabra L.) root, another product (ob- tained in 0.008 % yield) has been isolated from the acetylated- methylated mixture of sapogenins. The natural product, shown to be a carboxylie-dialcoholic triterpenoid, was isolated as the diacetate-methyl ester, m.p. 288-290 ~ [~]D+25.5 ~ (chloro- form), has the composition CasH520 v (high-resolution MS). That the gross carbocyclic system belongs to the oleanolic acid-glycyrrhetic acid type was revealed by the observation of IR bands (t385 and 1375 cm -1 (A region) and t325, 1308 and 1270 cm -I (t3 region) [3]). The only ethylenic content of the molecule is part of the ring-C c~fl-unsaturated ketone system as

evidenced by UV (max. at 247 rim, el4000), IR (t675 and 1625 cm -1) and NMR (sharp singlet at 65.64, C-12 proton) data. The MS revealed a close similarity between the fragmen- tion pattern of the isolated product and that of glycyrrhetic acid and its derivatives El, 4, 5,1. Specifically, there are ions indicating the presence of COO-Me and one OAc in the "right- hand" side of the molecule (at role 334 (90 %) comprising rings D, E and remnants of C derived from a retro-Diels-Alder fission across ring C, and at m/e 375 (100%) comprising rings C, D and E from a McLafferty rearrangement). Assuming the presence of a C-3/~ hydroxyl group, the second g r o u p - located on or around rings D and E - - i s evidently neither primary (NMR evidence) nor tertiary or axially bound. The latter conclusion is based on the observed facility of saponification of all ester groups where the rate of reaction was found to be comparable to that in methyl t 8~-glycyrrhetate acetate and in methyl liquiritate but distinctly higher than in methyl glycyrrhetate acetate. Since t S~-stereochemistry in the new compound is inferred from UV E6~ and NMR [7] data, it appears reasonable to conclude that the structure is related to liquiritic acid (18fl) ES~ rather than to glycyrrhetic acid (t 8fl). The precise Iocation and configuration of the additional (sec- ondary) hydroxyl group remains to be determined.

HOOC~

O~ ~ "~4s' ~ OH

However, after exclusion of the difficultly acyIable positions, it may be suggested that the group is most likely located at one of the possible t 5a, 16fl, 2 t or 22~ positions, giving structure I for the new triterpenoid of liquorice.

Received January 3 and February 7, t975

t. Elgamal, M. H.A. , Fayez, M. ]3. E., Snatzke, G.: Tetra- hedron 21, 2t09 (t965) ; Elgamal, M. H. A., Fayez, M. B. E. : Acta Chim. Acad. Sci. Hung. 58, 75 (1968)

2. Russo, G.: Fitoterapia 38, 98 (1967); Canonica, L., etal.: Gazz. Chim. Itat. 98, 7t2 (t968)

3. Snatzke, G., Lampert, F., Tschesche, R.: Tetrahedron 18, 14t7 (t962)

4. Budzikiewicz, H., Wilson, J .M., Djerassi, C.: J. Amer. Chem. Soc. 85, 3688 (1963)

5. Canonica, L., Russo, O., Bombardelli, E. : Gazz. Chim. Ital. 96, 832 (t966)

6. Beaton, J. M., Spring, F. S. : J. Chem. Soc. 1956, 2417 7. Mousseron-Canet, M., Crouzet, F., Chaband, J.-R.: Bull.

Soc. Chim. France 1967, 4668

T h e Z o o c h r o m e s of He l i c id She l l s

A. E. Needham

Department of Zoology, Oxford, England

The zoochromes of the shells of pulmonate gastropods are notoriously refractory to extraction and identification Eli, in sharp contrast to those of the primitive marine gastropods. Most pulmonate shells are a uniform brown, and the chrome responsible was called mel~nocochiin [2] because it resembles the melanins in colour and chemical intractability. Some helicids, such as Cepaea, have evolved quite a range of shell colours but these all have seemed equally refractory, implying a common origin from the melanoid chrome, like the range of colours in hair and feathers. They have attracted little attention E2, 3] therefore. Recent successes with vertebrate melanins L4] encourage a determined study of their moluscan analogues. This report deals with the shell chromes of Cepaea, brown, pink and yellow, all modulated in situ by an overlying dull yellow periostracmn. The simpler, dappled brown shell of Helix aspersa has been studied for comparison. In both genera the brown material is mainly in particular strata of the "pr i smat ic" layer of the shell. Decalcification by dilute acids frees it as microscopic flakes which are sepa- rated by centrifugation. From the washed centrifugate con- centrated HC1 extracts a bright yellow chrome with absorp- tion peaks at 2t6, 242, 275, 3t6 and 358 nm but this leaves

Naturwissenschaften 62 (1975) �9 by Springer-Verlag 1975 183