Nonstabilized N-unsubstituted azomethine ylides: a synthesis of indolizidine 239CD

[formula: see text] Treatment of a (2-azaallyl)stannane with HF.pyridine generated a nonstabilized N-unsubstituted azomethine ylide, which was found to undergo an efficient and stereoselective dipolar cycloaddition with phenyl vinyl sulfone to produce a trans-2,5-dialkylpyrrolidine that was further transformed into the dendrobatid alkaloid indolizidine 239CD.

Synthesis of the angiotensin converting enzyme inhibitor (-)-A58365A via an isomünchnone cycloaddition reaction

[formula: see text] The angiotensin converting enzyme inhibitor (-)-A58365A (1) was synthesized by a process based on the [3 + 2]-cycloaddition reaction of a phenylsulfonyl-substituted isomünchnone intermediate. The starting material for this process was prepared from L-pyroglutamic acid and involved using a diazo-phenylsulfonyl-substituted pyrrolidine imide. Treatment of the diazoimide with Rh2(OAc)4 in the presence of methyl vinyl ketone afforded a 3-hydroxy-2-pyridone derivative which was subsequently converted to the ACE inhibitor in six additional steps.

Exploration of beta-turn scaffolding motifs as components of sialyl Le(X) mimetics and their relevance to P-selectin

Monocyclic and bicyclic lactam units representing beta-turn surrogates were incorporated into a sialyl Le(X) structure by replacement of the natural sugar components. Low micromolar activity was found in a new P-selectin binding assay.

Biomimetic Diels-Alder cyclizations for the construction of the brevianamide, paraherquamide, sclerotamide, asperparaline and VM55599 ring systems

A potentially bio-mimetic Diels-Alder cyclization to construct the bicyclo[2.2.2] ring system common to the paraherquamides, marcfortines, sclerotamides, brevianamides, VM55599, and asperparaline is reported. Epi-deoxybrevianamide E (22) is converted into the corresponding lactim ether (23) and then oxidized with DDQ to provide an azadiene (24) which is tautomerized in the presence of base to azadiene 25 which, spontaneously cyclizes to give a 2:1 mixture of cycloadducts 26 and 27. These cycloadducts are each in turn, converted into D,L-C-19-epi-brevianamide A (20) and D,L-brevianamide B (6). The stereochemical implications of the [4 + 2] cycloaddition is discussed in the context of a working hypothesis on the biosynthesis of this family, particularly VM55599.

Design and synthesis of a new type of non steroidal human aromatase inhibitors

The structure-activity relationship study of one of recently described aromatase inhibitors, compound 1 (MR20814), allowed us to design some related derivatives as potential new inhibitors. Among those we synthesized, chlorophenylpyridylmethylenetetrahydroindolizinone 5 (MR20492) exhibited in vitro a ten-fold higher inhibition of the enzyme (IC50 = 0.2 +/- 0.0 microM and Ki = 10.3 +/- 3.3 nM).

Total synthesis of (+/-)-monomorine I and (+/-)-indolizidine 195B by an aza-[2,3]-Wittig rearrangement of a vinylaziridine

A novel synthesis of (+/-)-monomorine I (1) and (+/-)-indolizidine 195B (2) is described in which the key step is the highly efficient aza-[2,3]-Wittig rearrangement of vinylaziridine 12 into tetrahydropyridine 13. Functional group manipulation then gave ketone 16 which could be converted into the target alkaloids by reductive amination (1:2 1.5:1).

Castanospermine analogues: their inhibition of glycoprotein processing alpha-glucosidases from porcine kidney and B16F10 cells

We have used a simple and efficient procedure for the synthesis of N-5-carboxypentyl-1-deoxynojirimycin, an affinity ligand for alpha-glucosidase I (Bernotas, R. C. and Ganem, B., Biochem. J., 270, 539-540, 1990). The affinity gel was used to purify alpha-glucosidase I in one step from crude extract. In subsequent steps, partially purified alpha-glucosidase II was obtained. We have synthesized several analogues of castanospermine and studied their inhibition of alpha-glucosidase I in vitro using purified alpha-glucosidase I and in vivo in cultured B16F10 cells. Although the castanospermine analogues were significantly less active against the purified enzyme (IC50 approximately 1-23 micrograms/ml) as compared to castanospermine (IC50 = 0.02 microgram/ml), several compounds had up to 30-fold higher activity than castanospermine against alpha-glucosidase I in B16F10 cells, based on the accumulation of G3M7-9N2 oligosaccharide-containing glycoproteins. These results suggest that these analogues with lipophilic side chains cross the membrane barrier more efficiently than castanospermine. Once inside the cell, they may be converted to their active metabolite, castanospermine, by cellular esterases to give enzyme inhibition.

Novel heterocyclic analogues of the new potent class of calcium entry blockers: 1-[[4-(aminoalkoxy)phenyl]sulfonyl]indolizines

Several heterocyclic analogues of the potent 1-[[4-(aminoalkoxy)phenyl]sulfonyl]indolizines were synthesized and evaluated for their antagonistic calcium activities in comparison with the 1-sulfonylindolizine SR 33557 and the usual calcium antagonist references verapamil, cis-(+)-diltiazem, and nifedipine. The bicyclic nine-membered rings were, in general, more potent than the bicyclic 10-membered or five-membered rings. Among the bicyclic nine-membered rings, the indole nucleus appeared to be extremely favorable to support the calcium antagonistic activity. In particular, compound 36, with an IC50 value for the inhibition of [3H]nitrendipine equal to 0.072 nM, is among the most potent calcium antagonist known. This compound has been selected for clinical development.

2-Substituted 1-azabicycloalkanes, a new class of non-opiate antinociceptive agents

2-Substituted 1-azabicycloalkanes (3- and 5-aryloctahydroindolizines 2 and 11, 3-cyclohexyloctahydroindolizine 12, 4-aryloctahydroquinolizines 13, and 3-arylhexahydropyrrolizines 14) constitute a new class of non-opiate antinociceptive agents. These compounds demonstrated activity in the mouse abdominal constriction test and many were active in the mouse tail-flick test. trans-3-(2-Bromophenyl)octahydroindolizine (2a) did not bind to the opiate receptor nor did it affect arachidonate metabolism. 3-Aryloctahydroindolizines were prepared by catalytic hydrogenation of 1-aryl-3-(2-pyridinyl)-2-propen-1-ones. The X-ray crystal structure of (-)-2a was determined and absolute stereochemistry assigned as 3-R,8a-R.

A novel class of calcium-entry blockers: the 1[[4-(aminoalkoxy)phenyl]sulfonyl]indolizines

The synthesis and initial biological evaluation of a series of 1-sulfonylindolizines is described. These compounds have been shown to be representatives of a novel class of potent, slow-channel calcium antagonists. All compounds were found to be at least as active as the reference calcium antagonists verapamil and cis-(+)-diltiazem. Structure-activity relationship studies have shown that all compounds possessing an aralkyl group in the amine moiety and an isopropyl or cyclopropyl group at the 2 position of the indolizine are among the most potent calcium antagonists known outside the 1,4-dihydropyridine series. The IC50 values for the inhibition of [3H]nitrendipine binding vary between 0.19 and 4.5 nM whereas the IC50 value for nifedipine is 2.5 nM. One of the compounds in this group (9ab) has now been selected for clinical development.

Synthesis of the enantiomers of 6-epicastanospermine and 1,6-diepicastanospermine from D- and L-gulonolactone

The synthesis of the enantiomers of 6-epicastanospermine and of 1,6-diepicastanospermine from the enantiomeric gulonolactones is reported and the structure of the former is established as (1S,6R,7R,8R,8aR)-1,6,7,8-tetrahydroxyoctahydroindolizine. The inhibitory activities of the diastereomers against the amyloglucosidase-catalysed hydrolysis of p-nitrophenyl alpha-D-glucopyranoside were investigated, and the effects of 6-epicastanospermine and of 1,6-diepicastanospermine on 14 human liver glycosidases are reported.

5-Hydroxytryptamine (5-HT3) receptor antagonists. 1. Indazole and indolizine-3-carboxylic acid derivatives

Metoclopramide (1) is a gastric motility stimulant and a weak dopamine and 5-HT3 receptor antagonist. Conformational restriction of the (diethylamino)ethyl side chain of 1 in the form of the azabicyclic tropane gave 3, a very potent gastric motility stimulant and 5-HT3 receptor antagonist but devoid of significant dopamine receptor antagonist properties. Subsequent alteration of the aromatic nucleus led to the identification of indazoles 6a-h, and 1- and 3-indolizines 7b-d and 8, and imidazo[1,5-alpha]pyridines 9 and 10, as potent 5-HT3 receptor antagonists devoid of either dopamine antagonist or gastric motility stimulatory properties. Further conformational restriction of the side chain identified quinuclidine 11 and isoquinuclidine 12 as potent 5-HT3 receptor antagonists which mimic the distorted chair conformation of the tropane with, in the case of 11, the N-methyl group axial. From these series, 6g (BRL 43694) was found to be both potent and selective and has been shown to be a very effective antiemetic agent against cytotoxic drug induced emesis both in the ferret and in man.

Substituted benzamides with conformationally restricted side chains. 2. Indolizidine derivatives as central dopamine receptor antagonists

The substituted benzamides metoclopramide (1) and clebopride (3) are stimulants of gastric motility. They are also central dopamine receptor antagonists with 3 being the more potent. This is presumed to be due to an additional interaction of its N-benzyl group with the receptor. The effect of restricting the conformation of this group by replacing the N-benzylpiperidine side chain of 3 by phenyl-substituted quinolizidines and indolizidines has been investigated. Only the indolizidines had significant activity, the nature of which depended upon the orientation of the phenyl substituent. The 2 alpha-phenyl isomers 5d-h were potent central dopamine D2 receptor antagonists with 5h showing selectivity for the limbic system. The 2 beta-phenyl isomer 5c was a gastric motility stimulant devoid of significant central dopamine receptor antagonist activity. Implications on receptor models are discussed.

Indolizine derivatives with biological activity IV: 3-(2-Aminoethyl)-2-methylindolizine, 3-(2-aminoethyl)-2-methyl-5,6,7,8-tetrahydroindolizine, and their N-alkyl derivatives

In a continuing search for new biologically active agents derived from indolizine, 3-(2-aminoethyl)-2-methylindolizine, 3-(2-aminoethyl)-2-methyl-5,6,7,8-tetrahydroindolizine, and some mono- and di-N-substituted derivatives were prepared. Initial pharmacological screening showed that these compounds possess anti-5-hydroxytryptamine, antihistamine, antiacetylcholine, and CNS-depressant activities.

Indolizine derivativatives with biological activity III: 3-(3-Aminopropyl)-2-methylindolizine, 3-(3-Aminopropyl)-2-methyl-5,6,7,8-tetrahydroindolizine, and their N -alkyl derivatives

The syntheses and a preliminary pharmacological evaluation of some aminopropylindolizines and aminopropyltetrahydroindolizines are reported. All compounds showed anti-5-hydroxytryptamine, anti-histamine, and antiacetylcholine activities. Some also exhibited weak CNS activity.

Indolizine derivatives with biological activity II: N'-Substituted hydrazides of 2-methyl-3-indolizinecarboxylic acid

Synthesis and study of the antimonoamine oxidase activity of some N'-substituted hydrazides of 2-methyl-3-indolizinecarboxylic acid are reported. The activities were generally of about the same order as those of the corresponding hydrazides of 2-indolizinecarboxylic acid.