Rational Development of Practical Catalysts for Aromatic Carbon−Nitrogen Bond Formation

Simple indole alkaloids and those with a nonrearranged monoterpenoid unit

A series of C2-symmetric chiral quaternary ammonium bromides 10 and 11 have been designed as a new, purely synthetic chiral phase-transfer catalyst, and readily prepared from commercially available optically pure 1,1‘-bi-2-naphthol as a basic chiral unit. The details of the synthetic procedures of each requisite chiral binaphthyl subunit have been disclosed, and the structures of the assembled N-spiro chiral quaternary ammonium bromides 11a and 11f were unequivocally determined by single-crystal X-ray diffraction analysis. The reactivity and selectivity of these chiral ammonium bromides as chiral phase-transfer catalysts have been evaluated in the asymmetric alkylation of the benzophenone Schiff base of glycine ester 7 under mild liquid−liquid phase-transfer conditions, and the optimization of the reaction variables (solvent, base, and temperature) has also been conducted. Further, the scope and limitations of this asymmetric alkylation have been thoroughly investigated with a variety of alkyl halides, in...

Design of N-Spiro C2-Symmetric Chiral Quaternary Ammonium Bromides as Novel Chiral Phase-Transfer Catalysts: Synthesis and Application to Practical Asymmetric Synthesis of α-Amino Acids

Orally-active angiotensin-converting enzyme inhibitors are rapidly establishing themselves in the therapy of hypertension and congestive heart failure. Concerted efforts in a number of laboratories have now led to the discovery or synthesis of an unparalleled variety of potent inhibitors. The manner in which several of these inhibitors bind to ACE is beginning to be understood. It is hoped that some of the insights to be derived from the SAR and structural studies done with ACE inhibitors will be applicable to other enzyme targets as well. The success of ACE inhibitors as pharmacological tools and in the clinic will also quite certainly encourage future efforts to develop new enzyme inhibitor approaches to drug therapy.

Recent developments in the design of angiotensin-converting enzyme inhibitors.

The total synthesis of reserpine

The Stereochemistry of Reserpine, Deserpidine and Related Alkaloids1,2

Bei der Permanganatoxydation und der Kalischmelze der Reserpinsaure wurden 4-Methoxy-oxalylanthranilsaure und 5-Oxyisophtalsaure isoliert. Als Arbeitshypothese wird deshalb fur Reserpinsaure eine Yohimbanstruktur postuliert. Durch die obigen Abbauergebnisse ist die Stellung der einen Methoxylgruppe festgelegt, wogegen die Haftstellen der drei weiteren funktionellen Gruppen noch nicht gesichert sind.

On the constitution of reserpine from Rauwolfia serpentina Benth.

WE wish to describe briefly a convenient paper chromatographic separation and identification of pyridine derivatives in use in this laboratory for some time which employs a modification of the wellknown Konig colour-reaction1. Leifer et al.2. have recently described the paper chromatography of nicotinic acid and nicotinamide, but the more involved microbiological method was used for defining the spots. In this laboratory the solvent used for the development of the compounds listed in the accompanying table is n-butyl alcohol saturated with 1.5 N ammonia. After evaporation of the solvent at room temperature, the dry paper is placed for fifteen minutes in a closed glass cylinder containing a few crystals of cyanogen bromide. The vapour pressure of this substance is high enough to provide a sufficient concentration for the first phase of the Konig reaction. The paper is then sprayed with a 0.25 per cent solution of benzidine in 1 : 1 ethanolwater. Amounts down to 5γ can be detected easily. It should be pointed out that although nicotinic acid and iso-nicotinic acid cannot be distinguished on the basis of RF values, they can be distinguished by distinctive differences in colour. This technique should be generally applicable to all non-volatile pyridine derivatives giving a positive Konig colour-reaction.

Paper Chromatography of Pyridine Derivatives

Fur Reserpin und Deserpidin wird eine neue stereochemische Formulierung vorgeschlagen, die auf folgenden experimentellen Befunden beruht:

Charles F. Huebner

Papers

The Stereochemistry of Reserpine, Deserpidine and Related Alkaloids1,2

On the constitution of reserpine from Rauwolfia serpentina Benth.

Paper Chromatography of Pyridine Derivatives

Rauwolfia alkaloids XXI. The stereochemistry of reserpine and deserpidine

Rauwolfia Alkaloids. XVII. 3-Epi-α-yohimbine