C. Szantay

Synthesis and rearrangement of 13-thiaprostanoids

Abstract Thiaprostanoids 13 were prepared by conjugate addition of mercaptane 6 to cyclopentenones 12 and 20. Novel rearrangements of these compounds to 14 and 15 were interpreted as enolate induced [1,5]-sigmatropic shift on the corresponding dehydration products 16. Preparation of the various substrates and structural elucidation of new products are described.

Comparative study on separation of diastereomers by HPLC

SummaryReversed (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.

Novel molecular rearrangements of 4-hydroxy-2-cyclopentenones

Novel rearrangements of hydroxycyclopentenone derivatives 1 and 24 to 7,9,11 and 31,33,35 are reported. The stereochemistry of the rearrangement is interpreted as the result of synchronous enolate induced [1.5]-sigmatropic rearrangement and stepwise addition-elimination process. Preparation of the various substrates and structural elucidation of new products are also described.

Preparation and Separation of 1‐Methyl‐1,2,3,4‐tetrahydro‐β‐carboline Enantiomers by HPLC Using a New Derivatization Reagent

Abstract 1‐Methyl‐3,4‐dihydro‐β‐carboline (1) was C‐acylated with optically active sulfinyl derivatives (2) into the 1‐methyl group. Reduction of the C˭N double bond resulted in diastereomers (4, 5) of different ratios. After separation of diastereomers and removal of the chiral sulfinyl moiety, enantiomers of 1‐methyl‐1,2,3,4‐tetrahydro‐β‐carboline (6) were obtained from different enantiomeric excess. The diastereomers were separated by normal phase chromatography. It was proven that the resolution efficiency was much better with this type of separation method compared with very popular reversed phase chromatography. Embedded reversed phase column (Supelcosil ABZ + Plus) gave higher resolution than conventional C‐18 stationary phases and monoliths (Chromolith Performance RP‐18e), but retention time is high and low solubilities of derivatives caused detection problems and base line noise.

Efficient Synthesis of the Components of the German Cockroach Sex Pheromone I.

We wish to report ashort (6 steps) synthesis of sex pheromones of the German cockroach, the 3,11-dimethyl-2-nonacosanone (1) and the 29-hydroxy-3,11-dimethyl-2-nonacosanone (2) using the halopolycarbon homologation as the key step. The t-butyl-2-methyl-10-iodo-undecanoate (6) synthetized from 10-undecenoic acid (3) by methylation and iodination was coupled with the Grignard reagent derived from stearyl bromide (7) and 18-bromooctadecanyl-tetrahidro-2-pyranyl ether (8) in the presenee of dilithium tetrachlorocuprate. The natural pheromones (1 and 2) were finally obtained from the 2,10-dimethyl-octacosanon acid derivatives (11 and 12) with methyllithium in 230/0 (1) and 16010 (2) overall yields.