L. De Buyck

A Facile Synthesis of 1,2-Disubstituted Aziridines

Abstract In spite of the fact that a number of methods are available for the preparation of aziridines, general synthetic routes leading to 1,2-disubstituted aziridines remained laborious in most cases(2-6). A convenient and versatile synthesis is desirable in order to permit studies of this important biologically active heterocyclic system.

An efficient countercurrent distribution method for the large scale isolation of dimorphecolic acid methyl ester.

Abstract Effective procedures are reported for isolating and producing dimorphecolic acid (1) and its methyl ester (2) from Dimorphotheca pluvialis seed oil. The methods are suitable even for kilogram-scale production. The acid 1 was prepared by enzymatic hydrolysis of the oil and isolated by crystallization at low temperature. The ester (2) was obtained by methoxide-catalyzed transesterification of the glycerides followed by a countercurrent separation using four vessels and fourteen transfers with the two-phase system 90% aq. methanol-hexane. Methyl 9-oxo-10,12-E,E-octadecadienoate (3) (0.5 to 4%) was observed by GC and GC-MS and characterized by its reduction with sodium borohydride to racemic 2 and by its formation from 2 by Oppenauer oxidation. The complete assignment of the 1H and 13C-NMR signals of 1 and 3 has been carried out using 2D homonuclear and heteronuclear NMR experiments.

Selective oxidation of primary-secondary diols with methyl hypochlorite in acid buffered medium

Abstract A convenient, low cost method was developed for the selective oxidation of secondary alcohols, leaving primary alcohol functions intact. Methyl hypochlorite, generated from chlorine or trichloroisocyanuric acid in methanol, is used as a ‘positive chlorine’ reagent in the presence of an appropriate buffer which is acidic enough to warrant good transfer of ‘positive chlorine’. 1,9( R )-octadecanediol was converted to 1 -hydroxy-9-octadecanone with 98% selectivity.

SYNTHESIS OF THE 9-OXO-DIENE DERIVATIVE OF METHYL DIMORPHECOLATE BY AN EFFICIENT OPPENAUER OXIDATION PROCEDURE

Abstract Oxidation of methyl dimorphecolate (1) to methyl 9-oxo-10,12-E,E-octadecadienoate (2) has been studied, using Oppenauer conditions. Acetone and cyclohexanone have been used as oxidizing ketones. Combination of cyclohexanone with inert solvents has been performed to minimize the side reactions: degradation of the aluminum alkoxide catalyst and transesterification of the desired product (2). The optimal procedure is reported on 25 g scale using cyclohexanone (1.5 eq) and aluminum t-butoxide (0.2 eq) in hexane at 50°C (30 min).

Facile Synthesis of γ-Butyrolactones

Abstract During the course of our investigations concerning the synthesis of allylic bromides bearing two electron-Withdrawing groups, it has been observed that Knoevenagel condensation products derived from aliphatic aldehydes and active methylene functions showed a tendency to undergo ring closure.1

New synthesis of 2-substituted resorcinols

Abstract By aromatization of 2-methyl-, 2-benzyl- and 2-acetyl-2-chloro-1,3-cyclohexanedione in dimethylforamide-hydrogen chloride 25%, respectively 2-methyl-, 2-benzyl and 2-acetylresorcinol were obtained in high yields.

Industrially feasible preparations of methyl 9(R)-hydroxy and methyl 9-oxostearate from Dimorphotheca seed oil

Optimized procedures are described for the synthesis of methyl 9(R)-hydroxyoctadecanoate (2) and methyl 9-oxo-octadecanoate (3) based on Dimorphotheca pluvialis seed oil. Simple countercurrent separation and Oppenauer oxidation (benzoquinone, aluminum t-butoxide) were applied to prepare 2 and 3 in more than 90% yield. The procedures are potentially applicable on industrial scale and well suited for upgrading aged oils.

The regio- and stereoselectivity of the MCPBA-epoxidation of methyl dimorphecolate and derivatives

Abstract Methyl dimorphecolate (methyl 9(S)-hydroxy-10, 12-E,E-octadecadienoate) (1) was converted to resp. 9-methoxy (2), 9-trimethylsiloxy (3), 9-acetoxy (4), 9-chloroacetoxy (5) derivatives with reaction conditions optimized to high yields. The dienes were epoxidized with m-chloroperbenzoic acid to mono-oxiranes with excellent conversion (ratio C10–C11 epoxy to C12–C13: 90:10 for 9-hydroxy; 12:88 for 9-methoxy; 26:74 for 9-siloxy; 16:84 for 9-acetoxy; 17:83 for 9-chloroacetoxy). Methanolysis of a mixture of 9-chloroacetoxy oxiranes gave the 9-hydroxy mixture with 19:81 proportions of isomers. Analysis was based on 1H and 13C NMR-spectrometry including 2D techniques.

Volatile Fractions of Chamaecyparis lawsoniana (A. Murray) Parl, and Chamaecyparis pisifera (Sieb. et Zucc.) Endl. var. filifera. Identification of Oplopanonyl Acetate

ABSTRACT The volatile fractions of Chamaecyparis lawsoniana and C. pisifera, although qualitatively analogous and fairly rich in lLnon jne, were differentiated from each other by the absence of δ-3-carene and bornyl acetate in the former, and a moderate δ-3-carene and bornyl acetate content in the latter. Both contained appreciable amounts of the acetate of the relatively rare sesquiterpenoid oplopanone, and the diterpene hybaene, both of which were identified by1 H-,13 C-NMR and mass spectrometry. No character impact compound could be identified in the oils.