0-Lactone ring opening

Heteratisine, C22H33O5N, crystallises in prisms, has m.p. 262-7° (dec.), [a]f7° + 40° (MeOH), forms a hydrochloride, m.p. 265-270° (dec.), contains one methoxyl and one methylimino group, two active hydrogens and a lactone ring, opened by alkali and re-formed on acidification. In a later paper the same authors describe the isolation of benzoylheteratisine, C29H3,03N, m.p. 213-4°, [a]jf° + 73° (EtOH), which yields a hydrochloride, m.p. 218-221° (dec.), and is hydrolysed to benzoic acid and heteratisine the latter they suggest may not exist naturally in the plant but may be produced from benzoylheteratisine during extraction. 

Compound 4 exhibits considerable stability towards hydrolytic, lactone ring-opening.96-97 Thus, after 24 hours at 37°, 0.02 molar aqueous solutions of 4 contain only 5% of 2 and, at room temperature, equilibrium between 2 and 4 is only reached after several weeks.96... 

As with its hydrolytic, lactone ring-opening, compound 4 reacts106,107 rather slowly with methanol, with formation of an equilibrium mixture containing methyl D-glucopyranuronate (62) and 4 in the ratio of 3 1. Compound 62 is formed much more rapidly and in high yield, however, on treatment27,108 of 4 with methanol in the... 

In accordance with the different stabilities of 25, 26, and 33 toward hydrolytic, lactone ring-opening, on reaction with methanol catalyzed by weak bases, compounds 26, 33, and 25, in that order, afford110 decreasing proportions of the corresponding methyl D-glucofuranuronate derivatives 63, 64, and 65. All of these compounds... 

Treatment of carboxyaldehydes 252 with hydrazine hydrate in ethanolic KOH under refluxing conditions provides an easy entry to the novel imidazo[2,l-4][l,3]thiazole fused diazepinones 253 via lactone ring opening by intramolecular nucleophilic attack of the amino group of the intermediate hydrazone which could not be isolated (Equation 31) <2006TL2811>. 

Lactone ring opening can be both enzymatic and nonenzymatic, but it appears that the two mechanistic routes are seldom distinguished in metabolic studies [2], Thus, a number of the reports published on metabolism of lactones assume enzymatic hydration and do not examine what the relative contribution of nonenzymatic processes may be. Like for lactonization reactions, only very few in vitro biochemical studies address the question of relative enzymatic contribution and mechanism. 

Reductive y-lactone ring opening, with concomitant desilylation at the tertiary position by LiAlH4, gave triol 17 in 80% yield. Finally, acetonide formation followed by oxidation with tetra-n-propylammonium perruthenate/A-methylmorpholine / /-oxide oxidation, led to the target aldehyde 19 in 80% overall yield. 

Synthesis of Block and Graft Copolymers by Combination of (Di)lactones Ring Opening Polymerization with Other Living/Controlled Polymerization Processes... 

Ouhadi T, Hamitou R, Jerome R, Teyssie P (1976) Soluble bimetallic p-oxoalkoxides. 8. Structure and kinetic behavior of the catalytic species in unsubstituted lactone ring-opening polymerization. Macromolecules 9 927-931... 

A similar lactone ring opening is involved in the asymmetric synthesis of stereospecifically monodeuterated 1-aminocyclopropane-l-carboxylic... 

Groll M, Huber R, Potts BCM (2006) Crystal Structures of Salinosporamide A (NPI-0052) and B (NPI-0047) in Complex with the 20S Proteasome Reveal Important Consequences of (3-Lactone Ring Opening and a Mechanism for Irreversible Binding. J Am Chem Soc 128 5136... 

The mode of lactone ring opening depends on the kind of catalyst. It is characteristic that -lactone polymerisation with a catalyst containing a metal alkoxide active bond (Mt-X X = OR) involves C(0)-0 bond scission in the coordinating monomer (via the metal orthocarbonate species) with regeneration of the metal alkoxide active bond [scheme (7)] [87]. On the other hand, the application of a catalyst with a metal carboxylate active bond [Mt-X X = 0C(0)R] for -lactone polymerisation results in Cp — O bond scission in the coordinating monomer with regeneration of the metal carboxylate active bond [scheme (8)] [88-90],... 

Basler, B., Schuster, O., and Bach, T. (2005) Conformationally constrained p-amino acid derivatives by intramolecular [2 + 2]-photocycloaddition of a tetronic acid amide and subsequent lactone ring opening. Journal of Organic Chemistry, 70, 9798-9808. 

For reactions where the presence of strong acids may give undesirable side reactions, such as lactone ring-opening, pre-formed peracids such as MCPBA,251 permaleic acid,252 monoperphthalic253 or MMPP254 may be used as alternatives to distilled peracetic acid (Figure 3.55). 

Fig. 9 Grafting of acetyl protected sugars by lactone ring opening or hydrosilylation, followed by deprotection...

Groll M, Huber R, Potts BC. Crystal structures of Salinospo-ramide A NPI-0052 and B NPI-0047 in complex with the 20S proteasome reveal important consequences of beta-lactone ring opening and a mechanism for irreversible binding. J. Am. Chem. Soc. 2006 128 5136-5141. 

All that is taking place is ring expansion, lactone ring opening with decarboxylation, and finally a local oxidation of the carbon atom at which the sulfone substituent in II is placed. 

This is an exceptional case in view of the ease with which the -lactone ring opens under the influence of the most varied reactions. 

Dynamic kinetic resolution atroposelective lactone ring opening and its use in the synthesis of natural products and chiral auxiliaries 03T8291. 

Mei, Y., Kumar, A., and Gross, R.A. (2002) Probing water-temperature relationships for lipase-catalyzed lactone ring-opening polymerizations. Macromolecules, 35.14, 5444-5448. 

Ethyl glucoside as a multifunctional initiator for enzyme-catalyzed regioselective lactone ring-opening polymerization. J. Am. Chem. Soc.,... 

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