Gerhard Penn

Enzymatic resolution of norbornane-type esters

Abstract Chiral norbornane-type alcohols of high optical purity were prepared via enzymatic resolution of their racemic esters using lipases from Candida cylindracea and Pseudomonas sp. This method presents a short and efficient access to a number of chiral building blocks on a molar scale for the synthesis of optically active cyclopentane systems.

Reaktionen mit cyclischen Oxalylverbindungen, XXIV. Zur Reaktion von 4-Benzoyl-5-phenyl-furan-2,3-dion mit Phenylhydrazonen bzw. Phenylhydrazin

Abstract4-Benzoyl-5-phenyl-furan-2,3-dione (1) reacts with various phenylhydrazones2 at 60–80°C to the pyrazole carboxylic acid3 a, which then can be decarboxylated to 4-benzoyl-1,5-diphenyl-pyrazole (5).1 and phenylhydrazine combine again yielding3 a as the main product and the isomeric pyridazinone6 as by-product. At higher temperatures (120–140°C) the reaction of1 with2 a leads to the formation of dibenzoyl acetic acid hydrazide derivatives8.The structures of all products were confirmed by IR, MS,15N- and13C-NMR spectroscopic measurements, in the case of the pyridazinone6 also by an X-ray study.6 crystallizes with one moleDMSO monoclinically in space group P 21/n (Nr. 14) with 4 molecules6 andDMSO per cell.The reaction pathways leading to the compounds3, 6 and8 are discussed.

Enzymatic preparation of optically active 7-oxabicyclo[2.2.1] heptane derivatives

Abstract Enzymatic resolution of endo-7-oxabicyclo [2.2.1] hept-2-yl butyrates 3 and 5 using lipase from Candida cylindracea led to optically pure bicyclic alcohols and esters being important intermediates for the synthesis of biologically active compounds.

Reactions of cyclic oxalyl compounds — 38. New isoindigoide dyes from heterocyclic 2,3-diones — Synthesis and thermal rearrangement☆

Abstract The heterocyclic 2,3-diones 1 and 11 together with Lawesson reagent (LR) afford novel isoindigoide dyes 4 and 12 , respectively. 4a can thermally be isomerized into the pyrano[4,3-c]pyrane 6, accompanied by a significant hypsochromic shift which was corroborated by quantum chemical calculations. The phoshporanylidene derivative 13 was obtained via Wittig reaction of 1 . All structural assignments were based on X-ray studies of 4a and 13 .

Large scale preparation of (+)- and (−)-endo-norbornenol by enzymatic hydrolysis

Abstract A multigram preparation of (+)-(1 R ,2 R ,4 R )- endo -bicyclo[2.2.1]hept-5-en-2-ol ((+)-2) and its enantlomer (−)−2 with an optical purity of 90% and > 96%, respectively, was accomplished via enantioselective hydrolysis of (±)-5-endo-norbornen-2-ylacetate using lipase from Candida cylindracea .