The anionic peroxidase associated with the suberization response in potato (Solanum tuberosum L.) tubers during wound healing has been purified and partially characterized at the biochemical level. It is a 45-kD, class III (plant secretory) peroxidase that is localized to suberizing tissues and shows a preference for feruloyl (omethoxyphenol)-substituted substrates (order of substrate preference: feruloyl > caffeoyl > p-coumaryl Ϸ syringyl) such as those that accumulate in tubers during wound healing. There was little influence on oxidation by side chain derivatization, although hydroxycinnamates were preferred over the corresponding hydroxycinnamyl alcohols. The substrate specificity pattern is consistent with the natural substrate incorporation into potato wound suberin. In contrast, the cationic peroxidase(s) induced in response to wound healing in potato tubers is present in both suberizing and nonsuberizing tissues and does not discriminate between hydroxycinnamates and hydroxycinnamyl alcohols. A synthetic polymer prepared using E-[8-13 C]ferulic acid, H 2 O 2 , and the purified anionic enzyme contained a significant amount of cross-linking through C-8, albeit with retention of unsaturation.

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Two analogs of podophyllotoxin, with the same absolute stereochemistry as the natural product, have been synthesized from the cycloadduct between a-hydroxy-a'-phenyl-o-quinodirnethane and the furnarate of S-methyl lactate. After initial attempts to produce the cycloadduct from photochemically generated a-hydroxy-a'-phenyl-o-quinodirnethane failed, a study of the thermal generation and reaction of a-hydroxy-o-quinodirnethane with the fumarate and acrylate of S-methyl lactate was made. A comparison was made of the diastereoselectivity of these cycloaddition reactions to those previously reported, in which the o-quinodirnethane was generated photochemically. The a-hydroxy-o-quinodirnethane was produced both by the known thermolysis of benzocyclobutenol and by therrnolysis of l-hydroxy-l,3-dihydrobenzo[c]thiophene-2,2-dioxide. The diastereorneric excess for the cycloaddition reactions was found to be greater than 95% with modest (ca. 55%) isolated yields of the major cycloadducts. Following these model studies, it was found that a-hydroxy-a'-phenyl-o-quinodirnethane produced thermally from l-hydroxy-3-phenyl-1,3-dihydrobenzo[c]thiophene-2,2-dioxide could be added to the furnarate of S-methyl lactate with high diastereoselectivity and good yield. The product of this reaction was converted to the podophyllotoxin analogs 7 and 17. Utilisant le cycloadduit obtenu par condensation de I'a-hydroxy-a'-phtnyl-o-quinodirnkthane et du fumarate du lactate de S-rnCthyle, on a synthCtisC deux analogues de la podophyllotoxine possCdant la m&rne stCrCochirnie que le produit naturel. I1 n'a pas Ct C possible de produire le cycloadduit B partir de l'a-hydroxy-a'-phenyl-o-quinodimkthane obtenu photochirniquernent; on a donc utilist une rnkthode thermique pour gCnCrer I'a-hydroxy-o-quinodirnCthane et pour rCaliser sa rCaction avec le furnarate du lactate de S-rnCthyle. On a effectuk une cornparaison de la diastkrCosClectivitC de ces rCactions de cycloaddition avec celles rapportCes antkrieurernent, alors que 1'0-quinodirnethane avait CtC gCnerC d'une f a~o n photochirnique. L'-a-hydroxy-oquinodirnkthane a CtC obtenu par la thermolyse connue du benzocyclobutCno1 ainsi que par la therrnolyse du 1-hydroxy-1,3-dihydrobenzo[c]thiophkne-2,2-dioxyde. On a trouvC que l'excks de diastCrCornkres eit plus grand que 95% alors que le rendernent en cycloadduits principaux isolCs n'est que de 55%. A la suite de ces Ctudes rnodkles, on a trouvC que I 'a-hydroxy-a'-phCnyl-o-quinodirnkthane obtenu therrniquernent B partir du l-hydroxy-3-phCnyl-l,3-dihydrobenzo[c]thiophkne-2,2-dioxyde peut &tre addition& au furnarate du lactate de S-rnkthyle avec une excellente diasterkosklectivitC et un excellent rendernent. Le produit de cette rkaction peut &tre transform6 dans les analogues 7 et 17 de la podophyllotoxine.Mots clis : o-quinodirnkthanes, asyrnetrique, Diels-Alder, lactate, podophyllotoxine, lignane.[Traduit par la revue] Introduction The synthesis of aryl tetralin ligans such as dimethyl isolariciresinol or podophyllotoxin requires the stereoselective a...

Abstract:The asymmetric syntheses of two new spirolactones prepared in optically pure form from L-3-nitrotyrosine are described. The key step, an oxidative spiroannulation, was carried out on the optically active phenols 11a and 11b and afforded the new spirolactones 5a and 5b in 85% and 83% yields, respectively, as mixtures (3:1 dr) of diastereomers. The major diastereomers from these mixtures could be isolated in optically pure form by trituration using acetone-hexanes as the solvent. Thus, the optically active spirolactones (+)-5a (+ 92.8 o , c=0.125 acetone) and (+)-5b (+112.0 o , c= 0.125 acetone) were obtained after four synthetic steps from L-3-nitrotyrosine in 41% and 43% yield, respectively.

The preparation of the enantiomerically homogeneous bicyclic iodide 26 and its use as a key intermediate for the total syntheses of the cis-clerodane diterpenoids ( -)-agelasine A 5 and ( +)-(3R,4&5R,gS,9R, 10S)-3,4epoxyclerod-13-en-15,16-olide 6 are described. r'Members of the very large family of clerodane diterpenoids, 15 which share the general carbon skeleton 1, have been isolated 16 13 14 antiviral, from Collectively, been tested a wide antibiotic, exhibit the range relatively a antitumour of variety terrestrial1 small of number biological and and insect of marine' clerodanes activities, antifeedant organisms. including that prop-have 2 d7dFW 8 .-erties.'*2 However, it appears that most of the clerodanes that 5 55, 5406. 51,4941.