Furaneolo [4-hydroxy-2,5-dimethyl-3(2 H)-furanone (l)], a flavour component of pineapple and strawberry, has been prepared by a two-step synthesis starting with readily available 3-hexyne-2,5-diol.By the same method 4-hydroxy-5-methyl-3(2H)-furanone (2) and Z-ethyl-4-hydroxy-5methyl-3(2H)-furanone (3a) have been prepared from Z-pentyne-1,4-diol and 3-heptyne-2,5-diol, respcctively. Furaneol(1) [4-Hydroxy-2,5-dimethyl-3(2H)-furanon] ist in den fluchtigenAnteilen der Ananas [l] und Erdbeere [a] als Aroma-Spurenkomponente entdeckt worden. Ausserdem wurde der karamelartige Sinneseindruck gewisser thermisch behandelter Nahrungsmittel auf die Anwesenheit von Furaneol (1) zuriickgefuhrt [3]. Modellversuche [4-71 z, sowie theoretische Vorstellungen [9] [lo] sind entwickelt worden, um die Entstehung der beiden Hydroxyfuranon-Derivate 1 und 2 aus entsprechenden Zukkern erklaren zu konnen. Da Furaneol (1) wegen seiner vielseitigen organoleptischen 1 2 3 a 3 b Eigenschaften [ 10-131 eine zentrale Stellung in der Aromenchemie einnimmt, hat es bisher nicht an Versuchen zu seiner Darstellung gefelilt [4] [12] [14]. Einen praparativ 1) 2) Registered trade mark of Fivmenich S A . Nach K . Heyns cntsteht beim Erhitzen von D-GIUCOSC auf 300" zusatzlich zu den bekannten Pyrolyseprodukten [8] Furaneol(1) in Spurcn. Wir danken Herrn Prof. Heyns fur diesc private Mitteilung. OH OH OH 0 7 8 2 9 3 a Dieselbe Reaktionsfolge (Ozonolyse, Reduktion mit Triphenylphosphin und saurekatalysierte Cyclisation) wurde auch auf die zu 4 homologen Diole 7 [19] und 9 [18]iibertragen. Wahrend im Falle von 9 das entsprechende Homofuraneol (3a + b) in ,Achtung! Das Arbeiten in unpolaren Liisungsmitteln sollte vermieden werden, da sich das aus 1 gebildete Ozonid in der Reaktionslosung bereits unterhalb 0" ohne jede aussere Einwirkung explosionsartig zersetzt. Andere Verfahrensweisen vgl. unter [18]. 4,

No abstract

Alkylation at N-1 of the NAD+ adenine ring with 3,4-epoxybutanoic acid, followed by chemical reduction to the alkali-stable NADH form and alkaline Dimroth rearrangement, gave the NADH derivative alkylated at the exocyclic adenine amino group. Enzymic reoxidation of the latter derivative gave nicotinamide -6-(2-hydroxy-3-carboxypropylamino)purine dinucleotide, a functionalized NAD + analogue carrying an w-carboxyalkyl side-chain at the exocyclic adenine amino group. Carbodiimide coupling of the latter derivative to high-molecular-weight water-soluble (polyethyleneimine, polylysine) and insoluble (aminohexyl-Sepharose) polymers gave the corresponding macromolecularized NAD + analogues. These derivatives have been shown to be enzymically reducible. The polyethyleneimine and polylysine analogues showed a substantial degree of efficiency relative to free NAD+ with rabbit muscle lactate dehydrogenase (60 and 25% respectively) but a lower one with yeast alcohol dehydrogenase and Bacillus subtilis alanine dehydrogenase (2-7 %).The polyethyleneimine derivative entrapped in cellulose triacetate fibres together with the lactate dehydrogenase was operationally stable during repetitive use.

Reaction in dimethyl sulfoxide of nicotinamide 8-bromoadenine dinucleotide with the disodium salt of 3-mercaptopropionic acid afforded nicotinamide-8-(2-carboxyethylthio)adenine dinucleotide, a new NAD' analogue functionalized at the adenine C-8 position by an w-carboxylic side chain. Carbodiimide coupling of the latter derivative to high-molecular-weight water-soluble (polyethyleneimine, polylysine) and insoluble (aminohexyl-Sepharose) polymers gave the corresponding macromolecular NAD+ analogues. These derivatives have been shown to be enzymically reducible. The polyethyleneimine analogue showed a substantial degree of efficiency relative to free NAD ' with yeast alcohol dehydrogenase (47 %) but a considerably lower one with rabbit muscle lactate dehydrogenase (3 %); the polylysine analogue showed a low degree of efficiency with both enzymes (5 -6 %).The use in the industrial, analytical or biomedical field of enzymes immobilized by physical entrapment in porous structures permeable to low-molecularweight substrates and products is becoming increasingly interesting. However, this immobilization technique, to be economically applicable also to enzymes utilizing readily dissociable coenzymes (like the NAD' and NADP'-dependent dehydrogenases), requires coupling of the cofactor, through a stable linkage, to hydrosoluble polymers, in such a way as to assure retention of coenzymic activity. In fact, by entrapment in the porous structure of such a macromolecular soluble cofactor derivative together with the enzyme (or multienzyme system) its loss by diffusion is prevented, and the interaction between coenzyme and enzyme can be satisfactorily performed with both in solution.Recently the synthesis and coenzymic activity of macromolecular soluble NAD' [l -51 and NADP'[6] derivatives from these and other laboratories has been reported. In all these derivatives the site of attachment, through a suitable linkage, of the cofactor molecule to the polymer was the exocyclic adenine amino group (P). In pursuing our studies[4] on macromolecular soluble NAD + derivatives we were interested in synthesising new NAD' derivatives of this type attached at a different site of the adenine nucleus to the same polymers, and to compare their coenzymic efficiencies to the ones of the corresponding N6 derivatives.

Alkylation at N-1 of the FAD adenine ring with 3,4-epoxybutanoic acid gave 1-(2-hydroxy-3-~arboxypropyl)-FAD. Dimroth rearrangement of the latter afforded N6-(2-hydroxy-3-carboxypropy1)-FAD. Coupling of the two carboxylic FAD derivatives to polyethyleneimine gave the corresponding soluble macromolecular FAD analogues.Fluorescence and circular dicliroism determinations at neutral pH showed for the N-1 carboxylic derivative an open conformation, while for the corresponding N6 derivative a stacked one as for FAD.All the synthesized derivatives have been shown to reactivate Aspergillus niger glucose oxidase and hog kidney D-amino acid oxidase apoenzymes, affording holoenzymes whose activity relative to that of the corresponding natural holoenzymes ranged from 3 to 15% for the N-I derivatives and from 20 to 97% for the N 6 derivatives.Investigations by ultraviolet difference spectra on the interaction with apo-n-amino acid oxidase showed substantial similarities between tlie N 6 carboxylic derivative and FAD in the binding to the apoenzyme, while a completely different behaviour was observed for the N-1 carboxylic derivative. The D-amino acid oxidase apoenzyme, the holoenzyme and the glutaraldehyde-treated holoenzyme were entrapped each in cellulose triacetate fibres together with the polyethyleneimine N h derivative and beef liver catalase; the operational stability of the three recycling systems with DL-alanine as substrate was shown to be respectively 6, 5 and 12 times higher than the one found for the entrapped natural holoenzyme system.The recent rapid development of applied enzymology opens new perspectives also in the use of oxido-, reductases requiring dissociable cofactors, like nicotinamide proteins and some flavoproteins.Most of the work done by our and other laboratories [ l ] (and references quoted therein) in this field dealt with the chemical functionalization of the coenzymes NAD ' . and NADP', followed by coupling of these new analogues to soluble polymers in order to allow their repetitive uses as active, non-diffusible, cofactors for dehydrogenase systems entrapped in porous structures. However, to our knowledge, no cffort has been devoted previously to chemical modifications of FAD aimed at possible applications with FAD-dependent enzymes that do not bind the cofactor tightly, like D-amino acid oxidase and glucose oxidase (although dissociation of the coenzyme from these enzymes occurs not so readily as for the NAD' and NADP'-dependent dehydrogenases).