8-Lactone preparation

Jasmine lactone, preparation, 787 Jet fuel, autoxidation, 665 Jojoba oil, ozonized, 718 Juice, hydrogen peroxide content, 653... 

Lactones derived from 2-desoxysugars behave like normal lactones prepared from hexoses and pentoses. Rates of hydrolysis of 8-lactones are much greater than those of the Y-type. Whereas hydrolysis of... 

Cyclohexanone and cyclopentanone monooxygenases have been used in the microbial BV oxidation of prochiral bicycloketones. A significant difference in behaviour of [3.3.0] and [4.3.0] substrates has been analysed by high-level DFT calculations.345 Al-BINOL complexes catalyse the enantioselective BV oxidation of cyclobutanones to give the corresponding y-butyrolactones in up to 84% ee.346 Advances in the enantioselective metal-catalysed reaction have been reviewed, especially for lactone preparation.347... 

K. Bock, I. Lundt, and C. Pedersen, The base catalyzed rearrangement of some 6-bromo-2, 6-dideoxyaldono-1,4-lactones. Preparation of L-digitoxose, Acta Chem. Scand. B, 38 (1984) 555-561. 

Electrochemical synthesis of a-methylene-7-lactone preparation of 5-(4-chlorophenyl)-4,5-dihydro-3-methylene(3H)-furanone11... 

When ketopantoyl lactone prepared by method 6b was used, the reaction was complete in 2 hr. 

One of the most important methods for lactone preparation, and hence of the corresponding hydroxy acids (or halogeno acids, Section 5.14.1 above) is the Baeyer- Villiger rearrangment of cyclic ketones by the action of peracids. A wide variety of peracids have been used in this reaction but currently the reagents of choice are pertrifluoroacetic acid, m-chloroperbenzoic acid, and permaleic acid. The mechanism is formulated below for the conversion of an acyclic ketone into an ester. 

Pyrans and 8-lactones, preparation using Ni(0)-catalyzed reaction of acetylenes with C02 and aldehydes 90YGK362. 

Cyano halides, see Halo cyanides Cyanohydrins, see Hydroxy cyanides Cyanohydrin synthesis, 414, 604 Cyano iniides, preparation, 434 Cyano ketones, see Keto cyanides a-Cyano lactones, preparation, 534 Cyclodehydration of ketones and alcohols, 15, 843... 

Hydtoxy ketones, dehydration, 30 preparation, 130, 131, 164, 174 Hydroxy lactones, preparation, 334 Hydroxylamines, preparation, 633 o-Hydroxylamino cyanides, preparation, 6Q7... 

In the synthesis of n-altrose from D-ribose, first effected by Levene and Jacobs, the only crystalline intermediate was the characteristic calcium D-altronate -3.5 H2O. The sirupy lactone prepared from it was then reduced to n-altrose with sodium amalgam, as mentioned earlier in this review. Calcium n-altronate has been obtained from other sources also, such as the aluminum chloride rearrangement of the acetates of lactose, cellobiose and glucose and subsequent transformation of the neolactose, celtrobiose and altrose derivatives thus produced (see Section... 

S-Benzylthiuronium Salt of Diginonic Acid. Thirty-five milligrams of diginonic lactone prepared by bromine oxidation of the sugar is saponified in 3 cc. of 0.1 iV barium hydroxide solution by refluxing for thirty minutes on the steam bath. After cooling, the solution is neutralized with carbon dioxide, boiled for two minutes, filtered, and the filtrate is concentrated to dryness. The residue is taken up in 4 cc. of hot methanol and treated with a hot solution of 48 mg. of /S-benzylthiuronium sulfate in 1 cc. of methanol. After centrifuging from barium sulfate, the clear solution is concentrated to dryness. The residue crystallizes on the addition of acetone. The salt is purified by solution in the minimum amount of hot methanol followed by addition of 3 volumes of hot acetone. If necessary, the hot solution thus obtained is filtered, concentrated and seeded, with addition of more acetone if necessary. The salt crystallizes in rosettes of fine plates and melts at 137-138 after several recrystallizations in the same manner. 

Addition of a Lewis acid has been noted to improve the stereoselectivity (Table 12, entries 1-3). High stereocontrol is observed for products which can equilibrate via enolization (Table 12, entries 6-10) and for the sterically demanding sulfone derivative (Table 12, entry 4). Application of this methodology to EPC synthesis is illustrated by the use of lactones prepared in 8 to 9 steps from mannose (Table 12, entries 11-18)1 4. The stereochemical information within the reactive allyl ether moiety is faithfully transmitted and, remarkably, the Z geometry of the olefins is retained during formation of the vinylcyclopentanes. These more sterically hindered substrates may give mixtures of 5- and 7-membered rings (Table 12, entries 11,12, and 14-16). 

The crude 7-bromo lactone, prepared by iV-bromosuccinimide bromination of furo[3,4-b]-pyridin-5(7//)-one, reacts with hydrazine or methylhydrazine to give pyrido[2,3-r/]pyridazin-5(6/7)-one (3a) or its 6-mcthyl derivative 3b.8... 

---