Addition of silylated carbon nucleophiles to iminium and cyclic< i> N</i>-acyliminium ions promoted by InCl< sub> 3</sub>
ABSTRACT InCl3 was used as Lewis acid in the addition of silyl enolates and allyltrimethylsilane ... more ABSTRACT InCl3 was used as Lewis acid in the addition of silyl enolates and allyltrimethylsilane to aromatic aldimines and cyclic N-acyliminium ions derived from 5-acetoxylactams affording β-aminocarbonyl systems and allyl adducts, respectively, in reasonable to good yields. The diastereofacial selectivity of cyclic N-acyliminium ions was investigated.
The asymmetric synthesis of the (6R)-hydroxymethyl-5,6-dihydro-2H-pyran-2-one, a key intermediate... more The asymmetric synthesis of the (6R)-hydroxymethyl-5,6-dihydro-2H-pyran-2-one, a key intermediate in the formal synthesis of (R)-argentilactone, and the total synthesis of (R)goniothalamin are described. Our aproach involved the Lemieux-Johnson oxidative cleavage, enantioselective Keck allylation, ring-closing metathesis and Wittig olefination.
Addition of a Chiral Boron Enolate to Cyclic N-Acyliminium Ions. Stereocontrolled Synthesis of th... more Addition of a Chiral Boron Enolate to Cyclic N-Acyliminium Ions. Stereocontrolled Synthesis of the Pyrrolizidine Ring System.-The alkaloid pyrrolizidine ring system, e.g. (+)-hastanecine (X), is synthesized with control of the stereochemistry at C-1 by addition of a boron enolate from (S)-(IV) to an acyliminium ion formed in situ from (III) via the single stereoisomer (V).-(
A number of studies have proposed an anti-diabetic effect for tarchonanthuslactone based on its s... more A number of studies have proposed an anti-diabetic effect for tarchonanthuslactone based on its structural similarity with caffeic acid, a compound known for its blood glucose-reducing properties. However, the actual effect of tarchonanthuslactone on blood glucose level has never been tested. Here, we report that, in opposition to the common sense, tarchonanthuslactone has a glucose-increasing effect in a mouse model of obesity and type 2 diabetes mellitus. The effect is acute and non-cumulative and is present only in diabetic mice. In lean, glucose-tolerant mice, despite a slight increase in blood glucose levels, the effect was not significant.
Page 1. Copyright 1992 by The Humana Press Inc. All rights of any nature whatsoever reserved. 027... more Page 1. Copyright 1992 by The Humana Press Inc. All rights of any nature whatsoever reserved. 0273-2289/92/3303--0169502.00 Degradation of ~-O-4 Lignin Model and Related Compounds by the Ascomycete Chrysonilia sitophila (TFB 27441 Strain) ...
Addition of silylated carbon nucleophiles to iminium and cyclic< i> N</i>-acyliminium ions promoted by InCl< sub> 3</sub>
ABSTRACT InCl3 was used as Lewis acid in the addition of silyl enolates and allyltrimethylsilane ... more ABSTRACT InCl3 was used as Lewis acid in the addition of silyl enolates and allyltrimethylsilane to aromatic aldimines and cyclic N-acyliminium ions derived from 5-acetoxylactams affording β-aminocarbonyl systems and allyl adducts, respectively, in reasonable to good yields. The diastereofacial selectivity of cyclic N-acyliminium ions was investigated.
The asymmetric synthesis of the (6R)-hydroxymethyl-5,6-dihydro-2H-pyran-2-one, a key intermediate... more The asymmetric synthesis of the (6R)-hydroxymethyl-5,6-dihydro-2H-pyran-2-one, a key intermediate in the formal synthesis of (R)-argentilactone, and the total synthesis of (R)goniothalamin are described. Our aproach involved the Lemieux-Johnson oxidative cleavage, enantioselective Keck allylation, ring-closing metathesis and Wittig olefination.
Addition of a Chiral Boron Enolate to Cyclic N-Acyliminium Ions. Stereocontrolled Synthesis of th... more Addition of a Chiral Boron Enolate to Cyclic N-Acyliminium Ions. Stereocontrolled Synthesis of the Pyrrolizidine Ring System.-The alkaloid pyrrolizidine ring system, e.g. (+)-hastanecine (X), is synthesized with control of the stereochemistry at C-1 by addition of a boron enolate from (S)-(IV) to an acyliminium ion formed in situ from (III) via the single stereoisomer (V).-(
A number of studies have proposed an anti-diabetic effect for tarchonanthuslactone based on its s... more A number of studies have proposed an anti-diabetic effect for tarchonanthuslactone based on its structural similarity with caffeic acid, a compound known for its blood glucose-reducing properties. However, the actual effect of tarchonanthuslactone on blood glucose level has never been tested. Here, we report that, in opposition to the common sense, tarchonanthuslactone has a glucose-increasing effect in a mouse model of obesity and type 2 diabetes mellitus. The effect is acute and non-cumulative and is present only in diabetic mice. In lean, glucose-tolerant mice, despite a slight increase in blood glucose levels, the effect was not significant.
Page 1. Copyright 1992 by The Humana Press Inc. All rights of any nature whatsoever reserved. 027... more Page 1. Copyright 1992 by The Humana Press Inc. All rights of any nature whatsoever reserved. 0273-2289/92/3303--0169502.00 Degradation of ~-O-4 Lignin Model and Related Compounds by the Ascomycete Chrysonilia sitophila (TFB 27441 Strain) ...
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