Lactone - a-angelica

Reaction of PTAD with a-angelica lactone gives the pyrazolotriazole 97 via an acyl ene reaction,152 and reaction with 4,4-diethyl-3,5-dimethyl-4//-pyrazole 2-oxide gives 98 after heating.153 A mesoionic bicyclic system 99 is proposed as a product from the reaction of DEAZD with triethylborane.154... 

Scheme 1 Hypothetical formation of lactols and a-angelica lactones in Crematogaster ants...

In the latter compounds, the cross-conjugated dienone is replaced by a fu-ran ring conjugated to an E double bond. Biosynthetically, it is not known if these compounds arise from 1,4-dione precursors such as 138 by a Paal-Knorr type cyclization (Scheme 2) or from the a-angelica lactones 134 by reduction of the lactone carbonyl followed by loss of water. 

Levulinic acid, acting in its lactone form (XXXII) undergoes dehydration and two products have been obtained, - and /3-angelica lactones, (XXXVIII) and (XXXIX), respectively. a-Angelica lactone has been found to polymerize to a tacky resin by the catalytic agency of boron trifluoride. 

Schmitt und Schuerch (54) haben inden (XXVII), Mcthylcyclo-penten (XXVIII), 4,5-Dihyi-o-2-methylfuran (XXIX), a-Angelica-lacton (XXX) und 1-Cyanocyclopenten (XXXI) polymerisiert. Fiir die... 

The same authors could also attribute a structure to the m/z 98 molecular ion, which corresponds to a 60/40 mixture of molecular ions of a-angelica lactone and... 

MIKE/CAD spectra of m/z 98 ions (CjH Oj ) formed by pyrolysis of DNA and other m/z 98 ions produced from a-angelica lactone and furfuryl alcohol [253]... 

Levulinic acid and 1% syrupy HsP04 heated cautiously at 15 mm., and distilled -> a-angelica lactone. Y 95%.—This procedure is suitable for large batches. (J. H. Helberger, S. Ulubay, and H. Civele-koglu, A. 561, 215 (1949).)... 

H)-Furanone, 5-methyl- 4-hydroxy-3-pentenoic acid lactone a-angelica lactone ... 

Inhibition of chemical carcinogen-induced neoplasia by coumarins and a-angelica lactone Cancer Res. 39 27A09. 

Methylfuran-2(3//)-one (a-angelica lactone) reacts with PTAD by an ene-type reaction involving acyl group transfer to yield (355) (Equation (53)) <80JCS(Pi)843>. 

An attempt to convert methyl levulinate to vinyl levulinate was unsuccessful (Figure 2). Heating methyl ester with vinyl acetate in acidic mercuric acetate gave a-angelica lactone as the major product rather than the vinyl ester. Vinyl levulinate was previously prepared by the mercuric ion-catalyzed reaction of levulinic acid with vinyl acetate (id), so this older preparation will be used for future studies. a-Angelica lactone can also be prepared by dehydration of the acid without the use of vinyl acetate (/ 7). 

Moreover, in 1998 Ube Industries, Ltd. discovered that PC decomposition is suppressed by small quantities of additives (carboxylic acid vinyl esters, such as vinyl acetate (7) and divinyl adipate (8) vinyl carbonates, such as methyl vinyl carbonate (9) [50] carboxylic acid allyl esters, such as allyl acetate (10) allyl carbonates, such as allyl methyl carbonate (11) [51] and cyclic vinyl esters, such as a-angelica lactone (12) [52]). 

Replacement of f-butyl perbenzoate in the oxidation reaction by f-butyl hydroperoxide allows, in the presence of catalytic CuOTf-bis(oxazoline) complex, allylic peroxidation of cyclohexene (eq 127). While the yield is good (75%), the enantioselectivity is quite poor (9% ee). A similar trend (high yield, low ee) is observed for the peroxidation of cyclopentene, a-angelica lactone and allylbenzene. 

The first real trial of asymmetric polymerization of unsaturated cyclic monomers was reported by Shuerch et al [195]. Cyclic olefins (4,5-dihydro-2-methylfuran, indene, 1-methyl cyclopentene and a-angelica lactone) were polymerized using complexes of BF3 with asymmetric Lewis bases like 1-a-methylbenzyl alcohol, tosyl-1-valine or camphor. 

---