Reserpine: A Challenge for Total Synthesis of Natural Products

Organic reactions on alumina

Scots pine has been shown to produce a volatile bouquet that attracts egg parasitoids in response to oviposition of the herbivorous sawfly Diprion pini. Previous analyses of headspace volatiles of oviposition-induced pine twigs revealed only quantitative changes; in particular, the sesquiterpene (E)-b-farnesene was emitted in significantly higher quantities by oviposition-induced pine. Here we investigated whether (E)-b-farnesene attracted the egg parasitoid Chrysonotomyia ruforum. We tested the behavioural response of C. ruforum females to different concentrations of (E)-b-farnesene. Egg parasitoids did not respond to this sesquiterpene at either concentration tested. However, they did respond significantly to (E)-b-farnesene when this compound was offered in combination with the volatile blend emitted from pine twigs without eggs. This response was dependent on the applied concentration of (E)-b-farnesene. Further bioassays with other components [(E)-b-caryophyllene, d-cadinene] of the odour blend of pine were conducted in combination with the volatile blend from egg-free pine as background odour. None of the compounds tested against the background of odour from an egg-free pine twig were attractive to the egg parasitoid. These results suggest that the egg parasitoids responded specifically to (E)-b-farnesene, but only when this compound was experienced in the right context, i.e. when contrasted with a background odour of non-oviposition-induced pine volatiles.

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The significance of background odour for an egg parasitoid to detect plants with host eggs.

A catalytic asymmetric allylation of 3,4-dihydroisoquinoline was carried out with allyltrimethoxylsilane-Cu as the nucleophile in the presence of DTBM-SEGPHOS as the chiral ligand to afford corresponding chiral 1-allyltetrahydroisoquinoline derivatives in good yield and stereoselectivity. The allyl adduct thus obtained was applied to the synthesis of several isoquinoline alkaloids such as crispine A and homolaudanosine. The reaction was further used for the synthesis of the isoquinoline moiety of schulzeine A.

Catalytic asymmetric allylation of 3,4-dihydroisoquinolines and its application to the synthesis of isoquinoline alkaloids.

A highly efficient one-pot transformation of readily accessible furans into 4-hydroxy-2-cyclopentenones in H2O, using singlet oxygen as oxidant, has been developed.

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One‐Pot Transformation of Simple Furans into 4‐Hydroxy‐2‐cyclopentenones in Water

Reversed (RP-HPLC) and normal phase chromatographic (NP-HPLC) separations have been developed for diastereomers ofN-acyl-1-methyl-1,2,3,4-tetrahydo-β-carbolines which are acylated derivatives of simple natural β-carboline alkaloids. Separations of derivatives having different acyl moieties in theO,O-diacyl-tartaric acid ester subtituent differed remarkably. Little or no resolution in either NP-HPLC or RP-HPLC could be achieved with the diacetyl-tartrate derivative. Base-line separation by RP-HPLC but no separation by NP-HPLC was possible with the bulkier and more apolar dipivaloyl derivative. Retention order of the bis-benzoylated diastereomers was reversed and separation time increased dramatically by RP-HPLC. Good separation of the medium polarity, but rigid,N-camphanyl derivative by NP-HPLC has been achieved, whereas RP-HPLC could not be used for separation of these diastereomers. Separability of different diastereomers was highly dependent on polarity and rigidity of the derivatizingN-acyl moieties. Conformational analysis by molecular mechanics and comparison of the lowest energy conformational states of the diastereomers was applied to rationalise separation-retention behaviour of stereoisomers by RP-HPLC.

Cs. Szántay

Papers

Comparative study on separation of diastereomers by HPLC

Novel molecular rearrangements of 4 hydroxy 2 cyclopentenones

An improved synthesis of yohimbine dieckmann ring closure of unsaturated diesters

Synthesis of vinca alkaloids and related compounds. xiv. a new route to cyclopropane carboxylic acid derivatives

New Antitumor Hydroxymethyl Derivatives of Vinblastine.