Salo Gronowitz

Convenient Synthesis of Various Terheterocyclic Compounds by Pd(0)-Catalyzed Coupling Reactions

Various terheterocyclic compounds containing thiophene, furan, selenophene, pyridine and thiazole rings have been obtained by the Pd(PPh 3 ) 4 -catalyzed coupling of dihalo-substituted heterocyclic compounds with heterocyclic boronic acids, using sodium bicarbonate as base and a 1,2-dimethoxyethane ― water mixture as solvent

The effect of some additives on the Stille Pd0-catalyzed cross-coupling reaction

Abstract It has been found that the addition of cupric oxide to the cross-coupling reaction (Stille reaction) of 2-tributylstannylpyridine with various halobenzenes and heterocyclic halides leads to a much faster reaction and higher yields. This is also the case for the formation of thieno[3,2-h]-1,6-naphthyridine from 2-(2-trimethylstannyl-3-pyridyl)-1,3-dioxolane and t-butyl-N-(2-bromo-3-thienyl)carbamate.

Palladium-catalysed synthesis of heterocondensed pyrroles

Abstract The palladium-catalysed preparation of some heterocondensed pyrroles from ortho nitrogen containing hetaryl iodides and derivatives of propargyl alcohol is described.

A novel approach to bz-substituted tryptophans via Pd-catalysed coupling / annulation.

Abstract The Pd-catalysed preparation of bz-substituted tryptophans and their derivatives, starting from 2-iodoanilines and γ,δ-acetylenic amino acid derivatives, is reported.

Stereospecificity of hepatic lipases

Most studies on the positional specificity of triacylglycerol llpases have dealt with the susceptibility of hydrolysis of the ester bonds on the primary versus the secondary carbon atom ln the glycerol moiety. More recently, differences between the primary positions have been observed. Lipoprotein lipase from milk, adipose tissue and post-heparin plasma preferentially hydrolyses the ester bond in position 1, whereas lingual llpase cleaves the bond at position 3 faster [l-3]. Assman et al. [4] reported no stereospeciticity for another llpase in post-heparin plasma, the hepatic lipase. In principle it should be possible to distinguish between the two lipases in post-heparin plasma by comparing the stereospecific and non-stereospeciflc hydrolytic activities. Since the interest for such measurements is increasing [5] we decided to reinvestigate the stereospeciflcity of different hepatic lipases. Contrary to expectations the heparln-releasable liver lipase has the same specificity as lipoprotein lipase, whereas the lysosomal liver lipase was non-selective between positions 1 and 3.

Palladium-catalyzed coupling of heteroaryl alkylstannanes with heteroaryl halides in the presence of silver(I)oxide

Abstract The Pd-catalyzed coupling of heteroaryl trialkylstannanes with a variety of heteroaryl halides has been shown to be greatly promoted by silver(I)oxide

Absorption of synthetic, stereochemically defined acylglycerols in the rat.

The stereochemistry of fat digestion and absorption was investigated in rats with thoracic duct fistulas, after feeding synthetic triacylglycerol or alkyldiacylglycerol. After feeding 1,2-dilauroyl-3-oleoyl-sn-glycerol, dilauroyloleoylglycerol and lauroyldioleoylglycerol were the most abundant chyle triacylglycerols. Positional analysis of the fatty acid distribution and the absence of optical activity indicated that the following structures dominated:rac-1,2-dilauroyl-3-oleoylglycerol andrac-1,3-dioleoyl-2-lauroylglycerol. Therefore, the triacylglycerol resynthesized from 2-lauroylglycerol (precursor to 60% of chyle triacylglycerol) and other precursors was essentially racemic. Chyle phospholipids contained largely endogenous fatty acids, and the proportion of lauric acid was very low. A racemic mixture of 1,2-di[3H] oleoyl-3-tetradecyl-sn-glycerol and 1-tetradecyl-2,3-di[14C] oleoyl-sn-glycerol was absorbed to a lower degree than triacylglycerol. The appearance of oleic acid with different labels in chyle and intestinal lipids did not differ, indicating the absence of stereospecificity in fat digestion. Possible explanations for the low absorption are discussed.

Indole-3-pyruvic acid oxime ethers and thieno analogues by Heck cyclisation. Application to the synthesis of thia-tryptophans

Abstract N -allylation of N -BOC substituted o -iodo anilines ( 14a-e ) and thienoamines ( 16,18,20 ) employing methyl or benzyl oxime ethers of ethyl (E)-2-oxo-5-bromo-3-pentenoate 2a , followed by palladium-catalysed Heck cyclisation yielded oxime ethers of Bz-substituted ethyl indole-3-pyruvates ( 15a-f ) and thienopyrroles ( 17,19,21–23 ). Attempted conversion of 2a into the corresponding tosyl hydrazone or oxime resulted in formation of pyridazine ( 10 ) and oxazine ( 13 ) derivatives. The three possible isomers of thia-tryptophan were obtained as the ethyl esters from corresponding methyl oxime ethers by reduction of the oxime double bond.

Stereospecificity of different lipases

The stereospecificity of 4 lipases towards enantiomeric alkyldiacylglycerols and alkylmonoacylglycerols was investigated. No stereospecific breakdown of the former substrate was observed for lipases from pancreas,Rhizopus arrhizus, Pseudomonas fluorescens, or bile salt-stimulated lipase from human milk. All lipases degraded 2-oleoyl-3-tetradecyl-sn-glycerol faster than 1-tetradecyl-2-oleoyl-sn-glycerol. Among X-1-acyl-3-alkylglycerol isomers, 1-acyl-3-alkyl-sn-glycerol was preferentially attacked by the 3 first mentioned lipases. Possible mechanisms and metabolic implications for these stereospecificities are discussed.

Inverted reactivity of aryllithium derivatives V. On the syntheses of thiocyano-, phenylsulfinyl-, and phenoxy derivatives of thiophenes and furans

The reaction of some diheterocyclic iodonium salts with a variety of nucleophiles has been studied. The reaction was of preparative use for the syntheses of thiocyano, phenylsulfinyl and phenoxy derivatives of thiophenes and furans.