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Spectroscopic examination of some historical samples from the terpene collection of Prof. H. Wienhaus resulted in the structure elucidation of dieucarvelones A, B and C, products of treatment of eucarvone with zinc in alkali and in confirmation of the structure of α-amyrilene, a rearrangement product of α-amyrin. The relative stereochemistry of dieucarvelones A and C was established by X-ray crystallographic analyses.

The depsidone fumarprotocetraric acid as well as the depsides perlatolic and thamnolic acids are lichen secondary metabolites. Their first dissociation constants (pK(a1)) in methanol were determined to be 2.7 for perlatolic acid and 2.8 for fumarprotocetraric and thamnolic acids by UV spectroscopy. Lower pK(a1) values are, so far, not known from lichen substances. Several lichens producing at least one of these compounds are known for their outstanding tolerance to acidic air pollution. This is demonstrated by evaluating published pH preferences for central European lichens. The low pK(a1) values suggest that strong dissociation of the studied lichen substances is a prerequisite for the occurrence of lichens with these compounds on very acidic substrata, as protonated lichen substances of different chemical groups, but not their conjugated bases, are known to shuttle protons into the cytoplasm and thereby apparently damage lichens.

Lichen substances are shown to increase or to inhibit the adsorption of Fe at cation exchange sites. The influence on the adsorption strongly differs between individual lichen substances and is different for Fe2+ and Fe3+. These results add a new biological role to the known functions of lichen secondary metabolites. In an experiment with cellulose filters, which were soaked with acetone solutions of lichen substances and were then incubated with micromolar solutions of FeCl2 or FeCl3, many lichen substances were found to increase Fe3+ adsorption, whereas others had no effect. Most lichen substances had no effect on Fe2+ adsorption, but two were found to reduce and one to increase the level of adsorption. Lichens of Fe-poor and -rich sites contain lichen substances with different adsorption behavior towards Fe2+ and Fe3+. All the studied lichen substances, which only occur in lichens of Fe-poor sites, turned out to be effective Fe3+ adsorbents. Lichens of Fe-bearing rock and slag, however, were found to lack lichen substances, or to contain substances that did not adsorb Fe3+ and had no effect on Fe2+ adsorption, or thirdly, to contain substances that increased Fe3+ adsorption, but decreased Fe2+ adsorption. These results suggest that lichen substances do play a significant role in Fe adsorption in lichens and determine their tolerance to excess concentrations of Fe. Notwithstanding the strong correlation between the secondary chemistry of lichen species and their preference for Fe-rich or Fe-poor substrates, the postulated mechanism of temporary Fe adsorption by lichen substances has to be subject of future biochemical research.

Hauck & Huneck (2007) and Hauck et al. (2007) established that lichen secondary chemistry is related to metal absorption in the apoplast of lichens. Depsidones occurring in the medulla of the Mn2+ and Cu2+-sensitive epiphytic lichen Hypogymnia physodes were found to reduce the absorption of Mn2+ and Cu2+ at cation exchange sites (Hauck & Huneck 2007). Several lichen substances, belonging to the depsidones, depsides, anthraquinones, or pulvinic acid derivatives, are known to absorb Fe3+ (Engstrom et al. 1980; Hauck et al. 2007). Occurrence of such lichen substances in lichens of Fe-poor sites, but rarity in lichens from Fe-rich sites suggests that they promote the intracellular uptake of Fe3+ (Hauck et al. 2007). In Acarosporion sinopicae lichens specialized on Fe-rich rock and slag, only two efficient Fe3+ absorbers are known, viz. the depsidone norstictic acid and the pulvinic acid derivative rhizocarpic acid. Their occurrence in Acarosporion sinopicae lichens is attributed to the fact that they reduce the absorption of Fe2+ at cation exchange sites despite their high affinity to Fe3+ (Hauck et al. 2007). The observations by Engstrom et al. (1980), Hauck & Huneck (2007) and Hauck et al. (2007), which were made in experiments with isolated lichen substances, suggest that these secondary metabolites control metal homeostasis in lichens by reducing the absorption of selected metal ions in the apoplast and by promoting the uptake of Fe3+.

A new acorane-type sesquiterpenoid has been isolated from Finnish Barbilophozia barbata, together with one known dolabellane- and two known fusicoccane-type diterpenoids. B. hatcheri and Ptilidium ciliare afforded previously known barbatane-, daucane- and pinguisane-type sesquiterpenoids, as well as dolabellane- and fusicoccane-type diterpenoids. Their structures were identified by spectroscopic and X-ray crystallographic analyses.

The regioselectivity of deprotonation/alkylation reactions of η6-1,3-dimethoxybenzene-Cr(CO)3 (5), η6-1,3-dimethoxy-5-methylbenzene-Cr(CO)3 (6) and 2-substituted derivatives of these compounds was investigated. It is shown that the regioselectivity highly depends on the reaction conditions. For instance, deprotonation of η6-1,3-dimethoxy-2-(trimethylsilyl)benzene-Cr(CO)3 (10) with n-BuLi followed by silylation or methylation affords 4-substituted products while the use of LiTMP at −78 °C cleanly gives rise to 5-substituted products. The regioselective alkylation of complexes of type 6 at the 5-methyl group is easily achieved. The usefulness of the latter possibility is demonstrated in a synthesis of olivetol dimethyl ether (33).

A new myltaylane-type sesquiterpene alcohol and nine known sesquiterpenoids were isolated from Bazzania trilobata. The absolute stereostructure of (1S,4S)-cis-5-hydroxycalamenene was revised to be (1R,4R)-cis-5-hydroxycalamenene by the X-ray crystallographic analysis of its p-bromobenzoate derivative. Four previously known sesquiterpenoids were isolated from Porella canariensis, together with an artefact of a pinguisane-type sesquiterpene lactone. Their structures were determined by the use of extensive NMR techniques.

The structure of perrottetianal B, a sacculatane-type diterpene dialdehyde, which has previously been isolated from the liverwort Porella perrottetiana was revised to 15-hydroxyperrottetianal by the analysis of NMR spectra. The distribution of the known sesqui- and diterpenoids, as well as bis-bibenzyl derivatives, in Swiss liverworts Barbilophozia lycopodioides, B. floerkei and French B. barbata and Japanese Jungermannia comata is discussed. Perrottetin E, a cyclic bis-bibenzyl isolated from Jungermannia comata showed inhibitory activity for thrombin (IC50 18 μM).

The structure of the lichen pigment haemoventosin has been revised to 3,4,6,9-tetrahydro-5,10-dihydroxy-7-methoxy-3S-methyl-1,6,9-trioxo-1H-naphtho-[2,3-c]pyran (3), mainly on the basis of long-range δC/δH correlations observed in 2D HMBC NMR experiments and long-range δH/δD isotope effects observed in partial deuteriation experiments with 10-O-acetylhaemoventosin; ortho- and para-quinonoid structures were distinguished by means of the transacetylation inferred in the sodium dithionite reduction of 10-O-acetylhaemoventosin.

Three new clerodane- and one new halimane-type diterpenoids: ent-3β,4β-epoxyclerod-13E-en-15-ol; 3R ∗ , 4R ∗ - dihydroxyclerod -13E- en-15-al ; 3R ∗ , 4R ∗ - dihydroxyclerod -13Z- en-15-al ; and 3ξ-hydroxy-5(10), 13E-halimadien-15-al, were isolated from the German liverwort Jungermannia hyalina, together with the previously known clerodane-type diterpenoids ent-3β,4β-epoxyclerod-13E-en-15-al; ent-3β,4β-epoxyclerod-13Z-en-15-al and kolavenol. The structures were determined by extensive NMR techniques and chemical degradation.

The structure and relative stereochemistry of lepranthin from the lichen Arthonia impolita has been elucidated as 1 by NMR spectroscopy and X-ray analysis.

The anatomy, chemistry and developmental morphology ofAnamylopsora pulcherrima is investigated. Some characters, including the ascus structure, suggest a close affinity with theAgyriaceae. However, the chemistry and the pycnidial structure differ as well as the ascoma ontogeny.Anamylopsora has a gymnocarpous ascoma development and the ascogonia are produced in stipes.Trapelia coarctata, as a typical member of theAgyriaceae, shows a hemiangiocarpous ascoma ontogeny. The anatomical, chemical and ontogenetical characters of several families are compared withAnamylopsora and it is shown that the genus is best placed in a monotypic familyAnamylopsoraceaeLumbsch & Lunke, fam. nova, which is placed in theAgyriineae (Lecanorales).

Three rearranged ent -spiroeudesmane-type sesquiterpenoids, spirodilatanolides A, B and C, and two new ent -eremophilane-type sesquiterpenoids, dilatanolides A and B, were isolated from the European liverwort Frullania dilatata , together with the previously known ent -sesquiterpene lactones, (+)-frullanolide, critonilide and eremofrullanolide, and their structures determined by extensive NMR techniques and chemical degradation. There are two geographical races in F. dilatata .

The lichens Haematomma nemetzii, a Ramalina species, and Tornabena scutellifera from Turkey have been analysed chemically. Nemetzon is a new anthraquinone from the apothecia of Haematomma nemetzii.

Haemophaein, a metabolite of the lichen Phyllopsora haemophaea has been structurally elucidated as 1-(2',2'-dihydroxyheptyl)-3,6-dihydroxy-8-(2"-oxoheptyl)-dibenzofuran-2- carboxylic acid-9,2'-lactone

Secondary metabolites from Lichen, mainly phenolic compounds, have been analysed and identified using high performance liquid chromatography with a photodiode array detector. Components of lichen thalli were detected by characteristic ultraviolet spectra and relative retention times. Some new minor components have been found in several lichens.

The isomerization of roccellic acid to threo-roccellic acid has been investigated. Reduction of dimethyl roccellate with LiAlH4 gave the corresponding diol which yielded on oxidation with Jones' reagent two isomeric γ-lactones. 1-Methyl roccellic amide has been transformed by a photochemical reaction to the δ-lactone acaranoic acid. Two copper complexes of roccellimide have been prepared.

Aliphatic lichen acids can be transformed into their phenacyl esters which show strong absorption in the UV (ca. λ = 240 nm) and which can be used to detect these compounds following high performance liquid chromatography. Other suitable derivatives are the p-nitrophenyl and benzyl esters, as well as the benzoates of the alcohols prepared from the acids by reduction of the corresponding methyl esters with lithium aluminium hydride.

A method for the identification of secondary aromatic lichen substances using high-performance liquid chromatography (HPLC) with reversed-phase columns, gradient elution and benzoic and solorinic acids as standards has been developed. A retention index ( I ), calculated from the elution time of the appropriate peak with reference to the standards, is used in identification. I values are recorded for 331 compounds chromatographed in this standard system.

Three new longipinane-type sesquiterpenoids, 9,11α,14α-triacetoxymarsupellone, 9,11β,14α-triacetoxymarsupellone and 9,14α-diacetoxymarsupellone, were isolated from German Marsupella emarginata together with marsupellone and acetoxymarsupellone, and their structures determined by NMR techniques. ent -Nuciferal has been isolated from Gymnomitrion concinnatum . The distribution of the previously known sesquiterpenoids in German Scapania undulata and Russian S. uliginosa and M. emarginata are discussed.

Six liverworts belonging to the Lophoziaceae were investigated and six new compounds isolated and their structures determined by application of 2D NMR techniques or X-ray analysis. Setiformenol, isolated from Tetralophozia setiformis, is the first example of a cembrane-type diterpenoid from a liverwort.

The structures of the lichen chromones galapagin, lobodirin, mollin, and roccellin, specific com­ pounds of Roccellaceae (lichens), have been es­ tablished as 1, 2, 3, and 4, respectively, by NOE difference spectroscopoy.

Arthonin, a metabolite of the lichen Arthonia endlicheri has been structurally elucidated as (−)-N-benzoyl-L-valinyl N′-benzoyl-L-isoleucinate. The syntheses of arthonin and iso-arthonin [(−)-N-benzoyl-L-isoleucyl-O-benzoyl-L-valinol] are described. In memory to my dear friend Gunther Snatzke.

The structure of the lichen pigment haemoventosin has been revised to 3,4,6,9-tetrahydro-5,10-dihydroxy-7-methoxy-3S-methyl-1,6,9-trioxo-1H-naphtho-[2,3-c]pyran (3), mainly on the basis of long-range δC/δH correlations observed in 2D HMBC NMR experiments and long-range δH/δD isotope effects observed in partial deuteriation experiments with 10-O-acetylhaemoventosin; ortho- and para-quinonoid structures were distinguished by means of the transacetylation inferred in the sodium dithionite reduction of 10-O-acetylhaemoventosin.

A new myltaylane-type sesquiterpene alcohol and nine known sesquiterpenoids were isolated from Bazzania trilobata. The absolute stereostructure of (1S,4S)-cis-5-hydroxycalamenene was revised to be (1R,4R)-cis-5-hydroxycalamenene by the X-ray crystallographic analysis of its p-bromobenzoate derivative. Four previously known sesquiterpenoids were isolated from Porella canariensis, together with an artefact of a pinguisane-type sesquiterpene lactone. Their structures were determined by the use of extensive NMR techniques.

The regioselectivity of deprotonation/alkylation reactions of η6-1,3-dimethoxybenzene-Cr(CO)3 (5), η6-1,3-dimethoxy-5-methylbenzene-Cr(CO)3 (6) and 2-substituted derivatives of these compounds was investigated. It is shown that the regioselectivity highly depends on the reaction conditions. For instance, deprotonation of η6-1,3-dimethoxy-2-(trimethylsilyl)benzene-Cr(CO)3 (10) with n-BuLi followed by silylation or methylation affords 4-substituted products while the use of LiTMP at −78 °C cleanly gives rise to 5-substituted products. The regioselective alkylation of complexes of type 6 at the 5-methyl group is easily achieved. The usefulness of the latter possibility is demonstrated in a synthesis of olivetol dimethyl ether (33).

Lichen chemistry continues to be a flourishing branch of natural product chemistry. Since the last major review by Elix et al. in volume 35 of this series (274) many new and interesting lichen substances have been isolated and synthesized. This suggests that an update is desirable. As in the previous articles new methods for structure elucidation and synthesis, biosynthesis, chemotaxonomy and biological activities of lichen substances will be discussed. Some other relatively recent treatments of the subject need to be mentioned: A short chapter by Culberson and Elix (100) in Harborne’s Methods in Plant Biochemistry treated lichen constituents. Several minor reviews were published in 1984 (382), 1991 (385) and 1994 (386). Volume III of Galun’s Handbook of Lichenology (311) contains a chapter on chemical constituents of lichens including secondary metabolic products, storage products of lichens, carotenoids and phycobiliproteins.

Hypothallin, a metabolite of the lichen Schismatomma hypothallinum (Lecanactidaceae, Opegraphales) has been structurally elucidated as (-)-N-benzoyl-ʟ-phenylalaninyl-N′- benzoyl-ʟ-leucinate by NMR and MS and by synthesisᴅ

The isolation and spectroscopic characterization of (-)-allo-proto-lichesterinic acid from Cetraria komarovii is described. Proto-lichesterinic and allo-proto-lichesterinic acids are transformed into numerous nitrogen-containing derivatives and the isomerization of the dihydro acids is investigated.

Two new sesquiterpenoids, 4-methylazulene-1-carbaldehyde and 4-methylazulene-1-carboxylic acid, were isolated from cultures of Calypogeia azurea . Their structures were established by spectroscopic analysis. The sodium salt of 4-methylazulene-1-carboxylic acid was a naturally occurring water-soluble azulene that displayed anti-inflammatory and anti-ulcer activity.

† Background and Aims Many species of lichen-forming fungi contain yellow or orange extracellular pigments belonging to the dibenzofurans (usnic acid), anthraquinones (e.g. parietin) or pulvinic acid group. These pigments are all equally efficient light screens, leading us to question the potential ecological and evolutionary significance of diversity in yellow and orange lichen substances. Here the hypothesis is tested that the different pigments differ in metal-binding characteristics, which suggest that they may contribute to adaptation to sites differing in pH and metal availability. † Methods UV spectroscopy was used to study the dissociation and the pH dependence of the metal-binding behaviour of seven isolated lichen substances in methanol. Metals applied were selected macro- and micronutrients (Cu 2þ ,F e 2þ ,F e 3þ ,M g 2þ ,M n 2þ and Zn 2þ ). † Key Results All the pigments studied are strong to moderate acids with pKa1 values between 2.8 and 4.5. Metal complexation is common in the lichen substances studied. Complexation takes place under acidic conditions with usnic acid, but under alkaline conditions with parietin and most compounds of the pulvinic acid group. The pulvinic acid derivative rhizocarpic acid forms metal complexes both in the acidic and the alkaline range. † Conclusions Metal complexation by lichen substances could be a prerequisite for lichen substance-mediated control of metal uptake. Assuming such an effect at pH values where the affinity of the metal for the lichen substance is intermediate would explain the strong preference of lichens with usnic or rhizocarpic acids to acidic substrata. Moreover, it would explain the preference of lichens with parietin and some lichens with compounds of the pulvinic acid group either for nutrient-rich substrata at low pH or for calcareous substrata.

The secondary product pattern of 38 specimens of Lasallia brigantium (Zsch.) Llano, L. hispanica (Frey) Sancho & Crespo and L. pustulata (L.) Merat were investigated by HPLC. A c­ cording to previous publications gyrophoric acid, lecanoric acid and umbilicaric acid were detected. Additionally two further unknown depsides were found. The presence of the anthraquinone skyrin, new to Lasallia, was shown for L. hispanica and L. pustulata. Skyrin is not equally distributed within the thalli but mainly concentrated in the umbilicus. In L. hispanica skyrin is located in the epihymenium, too. A correlation between secondary product pattern and thallus size or light supply does not exist.

The aerial parts of Chrysanthemum lavandulifolium Mak. (Asteraceae) yielded three new acetylenes of the spiroacetal type 1-3, as well as two new germacranolides 4-5 and several known lactones.

Three new gymnomitrane sesquiterpenoids have been isolated from the liverwort Marsupella emarginata var. patens together with the known (−)-gymnomitrene and (−)-ar-curcumene. Their structures and absolute configurations have been determined on the basis of chemical and spectroscopic evidence as well as from the results of an X-ray analysis of a derivative. We also describe the ring expansion reaction of the gymnomitrane framework and the chemosystematics of the genus Marsupella.

Lichen substances are known to function as chelators of cations. We tested the hypothesis that lichen substances can control the uptake of toxic metals by adsorbing metal ions at cation exchange sites on cell walls. If true, this hypothesis would help to provide a mechanistic explanation for results of a recent study showing increased production of physodalic acid by thalli of the lichen Hypogymnia physodes transplanted to sites with heavy metal pollution. We treated cellulose filters known to mimic the cation exchange abilities of lichen thalli with four lichen substances produced by H. physodes (physodic acid, physodalic acid, protocetraric acid, and atranorin). Treated filters were exposed to solutions containing seven cations (Ca(2+), Cu(2+), Fe(2+), Fe(3+), Mg(2+), Mn(2+), and Na(+)), and changes to the solution concentrations were measured. Physodalic acid was most effective at influencing metal adsorption, as it increased the adsorption of Fe(3+), but reduced the adsorption of Cu(2+), Mn(2+), and Na(+), and to a lesser extent, that of Ca(2+) and Mg(2+). Reduced Na(+) adsorption matches with the known tolerance of this species to NaCl. The results may indicate a possible general role of lichen substances in metal homeostasis and pollution tolerance.

The liverwort, Plagiochila porelloides contained three new sesquiterpene esters, derived from the mono esterification of a 2,3-secoaromadendrane-type sesquiterpenoid by different fatty acids in addition to ent -spathulenol and plagiochiline D. Their structures were established by chemical and spectral means.

Three new rearranged ent-eudesmane-type sesquiterpene lactones, spirodilatanolides A (1), B (2) and C(3), and two new ent-eremophilane-type sesquiterpene lactones, dilatanolides A (4) and B (5), have been isolated and their absolute structures determined by extensive spectroscopic and X-ray crystallographic analyses.

A new bisabolane-type sesquiterpenoid julaceal has been isolated from Anthelia julacea, together with the known terpenoids, ent-(−)-nuciferal

The structure of crustinic acid extracted from Umbilicaria crustulosa has been elucidated as 4,6-dihydroxy-3-carboxy-2-methylphenyl lecanorate by spectroscopic and chemical means.

Lichen chemistry continues to be a flourishing branch of natural product chemistry. Since the last major review by Elix et al. in volume 35 of this series (274) many new and interesting lichen substances have been isolated and synthesized. This suggests that an update is desirable. As in the previous articles new methods for structure elucidation and synthesis, biosynthesis, chemotaxonomy and biological activities of lichen substances will be discussed. Some other relatively recent treatments of the subject need to be mentioned: A short chapter by Culberson and Elix (100) in Harborne’s Methods in Plant Biochemistry treated lichen constituents. Several minor reviews were published in 1984 (382), 1991 (385) and 1994 (386). Volume III of Galun’s Handbook of Lichenology (311) contains a chapter on chemical constituents of lichens including secondary metabolic products, storage products of lichens, carotenoids and phycobiliproteins.

The volatile part of Agastache rugosa, (Labiatae) contains more than 90% of methyl chavicol. The fresh, herbaceous, spicy odor of the ground leaves was therefore caused by methyl chavicol in combination with some minor constituents such as anisaldehyde and p-methoxy cinnamaldehyde.

The structures of the lichen chromones galapagin, lobodirin, mollin, and roccellin, specific com­ pounds of Roccellaceae (lichens), have been es­ tablished as 1, 2, 3, and 4, respectively, by NOE difference spectroscopoy.

Lichens, symbiontic organisms of fungi and algae, synthesize numerous metabolites, the "lichen substances," which comprise aliphatic, cycloaliphatic, aromatic, and terpenic compounds. Lichens and their metabolites have a manifold biological activity: antiviral, antibiotic, antitumor, allergenic, plant growth inhibitory, antiherbivore, and enzyme inhibitory. Usnic acid, a very active lichen substance is used in pharmaceutical preparations. Large amounts of Pseudevernia furfuracea and Evernia prunastri are processed in the perfume industry, and some lichens are sensitive reagents for the evaluation of air pollution.