Establishment of a Molding Procedure to Facilitate Formulation Development for Co-extrudates.

Co-extrusion offers a number of advantages over conventional manufacturing techniques. However, the setup of a co-extrusion line is cost- and time-intense and formulation development is challenging. This work introduces a novel procedure to test the applicability of a co-extruded reservoir-type system at an early product development stage. We propose vacuum compression molding (VCM), a fast procedure that requires only small material amounts, for the manufacturing of cylindrical reservoir-type system. To this end, the commercially available co-extruded product NuvaRing® and variations thereof were used as test systems. All VCM systems showed a homogeneous skin thickness that adhered well to the core, thereby providing a precise core/skin interface. As drug release is a key criterion for pharmaceutical products, a modified in vitro dissolution method was set up to test the VCM systems. The drug release from the VCM systems was in the same order of magnitude as the corresponding co-extruded strands and followed the same release kinetics. Moreover, the VCM systems were capable of indicating the relative effect of formulation-related modifications on drug release. Overall, this shows that this system is a powerful tool that facilitates formulation tailoring and co-extrusion process setup at the earliest stage.

Enantioselective total synthesis of the oral contraceptive desogestrel by a double Heck reaction.

A novel enantioselective total synthesis of the oral contraceptive desogestrel (2) is described, in which the tetracyclic steroid core is formed by a sequence of two consecutive Heck reactions. Conversion of the known enantiopure diketone 7 led to the chiral bicycle 6 which was used for a diastereoselective intermolecular Heck reaction with vinyliodide 5 to give 15. In the following intramolecular Heck reaction, the tetracyclic ring system was formed to give 4, from which the synthesis of desogestrel (2) was furnished.

Crystal structures of 10alpha-gon-5-enes from the synthetic pathway to desogestrel.

X-ray crystallographic studies performed on the product of the ketalization reaction of 13beta-ethyl-11alpha-hydroxy-gon-5-ene-3,17-dione have lead to the unequivocal assignment of the 10alpha stereochemistry to C10, showing that an inversion of configuration occurred during formation of the 3,17-diketal. From the Swern oxidation of this compound, 11alpha-(methylthio)methoxy-10alpha-gonene was obtained as the major product instead of the desired 11-ketone. Modeling studies showed that the configurational instability at C10 is determined by the presence of the 11alpha-hydroxyl group.

Simple, catalytic enantioselective syntheses of estrone and desogestrel.

Highly enantioselective and very short syntheses of the bioactive forms of estrone (3) and desogestrel (4) are described using a chiral oxazaborolidinium catalyst (2) in the key initial step. Enantiomerically pure estrone was synthesized in eight steps from the readily available starting materials diene 5 and alpha,beta-enal 6 via intermediates 8 and 9. Desogestrel was synthesized using a similar strategy from diene 5 and alpha,beta-enal 11 via intermediates 12-17. The efficient syntheses of the chiral catalyst 2 and its enantiomer are also presented.

Base promoted air oxidation of 13beta-ethyl-11-methylenegon-4-en-17-one.

The structure of 13-ethyl-11-methylene-18,19-dinor-17alpha-pregn-4-en-20-yn-16beta,17-diol (3, 16beta-OH desogestrel), a by-product obtained in the last step of the synthesis of desogestrel (1) by reaction of monolithium acetylide-ethylenediamine complex with 13beta-ethyl-11-methylenegon-4-en-17-one (2), is here reported. The structural assignments were supported by NMR 1H-, 13C-, 1H-1H COSY, 1H-13C HSQC, COLOC) and mass spectroscopy, and the configuration at the C-16 and C-17 stereocentres was established by X-ray crystallography. When the same 17-ketoderivative 2 was treated with a non-alkylating base, such as potassium tert-butoxide, instead of the expected 16-hydroxylated ketone, a dimeric product, 13beta-ethyl-16-[2'-(des-D-13"-carboxy-13"beta-ethyl-11"-methylenegon-4"-en-14"-yl)-ethyliden]-11-methylenegon-4-en-17-one (4), was isolated in good yield; it was characterized by NMR, mass, ultraviolet spectroscopy, and chemical transformations. Compounds 3 and 4 originate from the high reactivity of the 16-methylenic position of the 17-keto substrate (2) toward molecular oxygen under basic conditions.

Reduction of aromatic steroidal A rings by lithium in ethyl amine.

The reduction of 3-methoxy-estra-1,3,5(10)-trien-17beta-ol (6) and 13-ethyl-3-ethoxy-gona-1,3,5(10)-triene-11alpha,17beta-diol (2) by lithium in ethyl amine in the absence of a proton source is described. Both reductions, contrary to the reports of previous investigators, which indicated the 4-ene to be the main reaction product, gave a complex mixture of products. In the case of the reduction of 2, which is an intermediate in the synthesis of the progestagen desogestrel (1), we obtained the expected known 13-ethyl-gona-4-ene-11alpha,17beta-diol (4) in small amounts and three new steroidal monoenes, 13-ethyl-gona-5(10)-ene-11alpha,17beta-diol (11), 13-ethyl-gona-5(6)-ene-11alpha,17beta-diol (12), and 13-ethyl-gona-1(10)-ene-11alpha,17beta-diol (13). These compounds were characterized as the 11,17-diacetates with the 5(10)-ene 11 being the major compound.

The remarkable influence of steroid A/B-ring junction on the Wittig olefination reaction of the 11-oxo group: towards the synthesis of 5 alpha- and 5 beta-oriented delta 3-isomers of desogestrel.

The 5 alpha- and 5 beta-oriented delta 3-double bond isomers 8, 9 of the widely used progestin desogestrel (7) were synthesized. Wittig olefination reaction of the 5 alpha-intermediate 12 showed a dramatically reduced reaction rate compared with the olefination of the 5 beta-intermediate 13. Computational studies suggest that different energies of the intermediary 1,2-oxaphosphetanes may, at least partially, have been the reason for this phenomenon.