A. Messmer

Unprotected sugar phosphinimines: A facile route to cyclic carbamates of amino sugars

Abstract Unprotected sugar phosphinimines were prepared from various azido sugars by reaction with triphenylphosphine and were converted by carbon dioxide into cyclic carbamates of amino sugars. The reaction could be carried out more conveniently in a one-pot process without isolation of the phosphinimines. The 13 C-and 31 P-n.m.r. data for N -(β- d -glucopyranosyl)triphenylphosphine imide ( 2 ) revealed an unexpected conformation of the phosphinimine moiety (proposed as a “reverse exo-anomeric effect”) stabilised by an interaction with HO-2.

Synthesis of novel ellipticine analogues and their inhibition of Moloney leukaemia reverse transcriptase

Abstract Two new ellipticine analogues were synthetized as potential non nucleoside inhibitors of reverse transcriptase and were tested on Moloney leukaemia virus reverse transcriptase in vitro. Both derivatives (9a,b) showed considerable inhibitory effect; ID50 was found to be in the range of 2.8 to 4.5 × 10−5 M.

A new route to cyclic urea derivatives of sugars via phosphinimines

Abstract Sugar phosphinimines and the corresponding aminophosphonium salts were prepared from 2-amino-2-deoxy- d -glucosyl azide derivatives and their structures were established by 13 C- and 13 P-n.m.r. spectroscopy. A simple one-pot procedure, involving reaction of the azides with triphenylphosphine and carbon dioxide, provides an efficient access to cyclic urea derivatives.

The stereochemistry and mechanism of the ring opening reaction of 3-aryltetrazolopyridinium salts and their v-triazolo analogues

Abstract Contrary to earlier reports, the title reaction was found to yield both 1E and 1Z configured dienic products predicted for a disrotatory process. A novel degradation giving, via the loss of one carbon unit, tetrazolyl- and triazolyl-acrolein was also observed.

Synthesis and nitrogen elimination of 3-aryltetrazolo(1,5-a)pyridinium salts and its angular benzenologues

Abstract 2-Pyridyl aryltriazenes ( 2 ) as well as 1-isoquinolyl-, 2-quinolyl - and 6-phenanthridyltriazenes ( 6 , 9 , 12 ) undergo cyclization in the presence of 2, 4, 4, 6-tribromocyclohexa-2, 5-dien-1-one ( 3 ) and result in 3-aryltetrazolo (1, 5-a) pyridinium salts ( 4 ) and its angular benzenologues ( 7 , 10 , 13 ). These new tricyclic ( 7 , 10 ) and tetracyclic ( 13 ) angularly fused tetrazolium salts when treated with tetraalkylammonium hydroxide result in rapid nitrogen elimination under mild conditions and give rise to N-aryl-aminoisoquinolones, -quinolones and -phenanthridones ( 14 , 15 , 16 ). In the case of the bicyclic tetrazolo (1,5-a) pyridinium salts ( 4 ) a nitrogen elimination reaction - analogous to that found with the tricyclic tetrazolium salts - can, however, be observed only by using alkoxides as reagents: thus, tetrazolyldieneethers ( 18 ) and N-arylaminopyridones ( 19 ) are simultaneously formed.

Ring opening of [1,2,3]triazolo[1,5-a]pyrazinium salts: Synthesis and some transformations of a novel type of 2-aza-1,3-butadienes

Abstract The synthesis of 1,3-disubstituted [1,2,3]triazolo[1,5-a]pyrazinium salts 6 and subsequent ring opening induced by the reaction with pyrrolidine provides a facile access to 4-(1-pyrrolidino)-1-([1,2,3]triazol-5-yl)-2-aza-1,3-butadienes 7, a new type of 2-aza-1,3-butadienes. Compounds 7 proved to be suitable starting materials for further ring formation reactions.

Formation of 2,5-anhydro derivatives in the zemplén de-acetylation of acetylated sugar formazans

Abstract Deacetylation of acetylated d -galactose and 6-deoxy- d -galactose diphenylformazans under Zemplen conditions required much more (1.1 mol.) than the usual catalytic amount of sodium methoxide to complete the reaction, and 2,5-anhydro- d -talose diphenylformazans were obtained. The structure of the products was proved by 1 H- and 13 C-n.m.r. spectroscopy, and a mechanism for the reaction is suggested.

Selective ring opening of linearly and angularly fused triazolium salts

Abstract Angularly and linearly fused 1.2-. and 1.3-disubstituted [1,2,4]triazolium salts were synthesised and reacted with nucleophiles. The sites of attack were found to depend both on the type of annelation and substitution pattern: the linearly fused derivative reacted at the pyridine moiety, whereas the angularly condensed salts were attacked at one of the carbon atoms of the triazole ring, and subsequent ring openings occurred in both cases. For the experienced ambident reactivity a general mechanistic scheme was proposed and the annelation-dependent regioselectivity was rationalised on the basis of an MO approach.

Cycloadditions with hetaryl dieneamines a direct route to hetarylazulenes

Hetaryl dieneamines readily available from fused N-aryl azolium salts with secondary amines were found to undergo cycloadditions. With N-phenylmaleinimide and acetylene dicarboxylic ester, [4+2] cycloaddition took place to yield tetrahydroisoindolone (2) and phtalic acid (3) derivatives, respectively. Reaction with fulvene reagent4 resulted in a [6+4] cycloaddition followed by a spontaneous elimination and allowed a convenient route to hetaryl azulenes (5–7).AbstractDie aus kondensierten N-Aryl-azoliumsalzen leicht zugänglichen Hetaryldienamine gehen Zykloadditionen ein. Mit N-Phenylmaleinimid und Acetylendicarbonsäureester traten [4+2]-Zykloadditionen ein, wobei Tetrahydroisoindolon- (2) und Phtalsäurederivate (3) erhalten wurden. Die Reaktion mit Fulvenreagenz4 führte zu einer [6+4]-Zykloaddition und anschlieβender spontaner Eliminierung; das erwies sich als eine bequeme Route zu Hetarylazulenen (5–7).

Synthesis and nitrogen elimination of the linearly fused tetrazolo (1 ,5-b) isoquinolinium salts : Formation of a new tetracycle: Indazolo (2,3-b) isoquinoline

Abstract Treatment of 3-aminoisoquinoline ( 1 ) with aryldi-azonium salts gave 2-amino-4-arylazoisoquinolines ( 2 ) which reacted with aromatic aldehyde to yield imidazo(4,5-c) iso-quinolines. With 3-amino-4-methylisoquinoline ( 4 ), however, the same reaction led to 3-isoquinolyltriazenes ( 5 ), and these could then be cyclized by the use of “TBB” to give tetrazolo(1,5-b)-isoquinolinium salts ( 6 ). The latter azolium salt ( 6 ) showed ambident reactivity in the presence of hydroxide ion manifested by simultaneous formation of tolualdehyde derivative 10 and indazolo (3,2-b) isoquinoline system ( 8 ). This ambidency as well as the difference in behaviour between the new linearly fused system ( 6 ) and its formerly studied angularly fused isomers (“annelation effect”) is interpreted in terms of the frontier molecular orbital theory.