Marasmane lactones

Flavidulol D was isolated from L. flavidulus, and its structure was identified as the stearate of flavidulol A (22.8) on the basis of spectroscopic data (147). The new marasmane lactone P3 and diketopiperazine P4 were isolated from the most polar fraction of an ethanolic extract of L. vellereus (148). The structures of compounds P3 and P4 were established by extensive NMR studies together with acetylation reactions. The isolation of lactone P3 suggested that the possible oxidation of the 15-methyl group, typical of a few lactarane sesquiterpenes, could take place at the early velutinal stage... 

Daniewski, W.M., M. Gumulka, K. Ptaszynska, P Skibicki, J. Krajewski, and P. Gluzinski Marasmane Lactones from Lactarius vellereus. Phytochemistry, 31, 913 (1992). 

The following y-lactone sesquiterpenoids with the parent marasmane skeleton have also been isolated from L. vellereus 13-OH-7(8)-en (7.1) (33), 7a,8a,13-tri-OH (7.18) (33), 7a,8p,13-tri-OH (7.19) (41), and 9a,10a,13-tri-OH-7(8)-en (7.16) (32) marasman-5-oic acid y-lactones. Their structures have been established by spectroscopic data of the natural products and of their acetyl... 

The group of heterocyclic marasmane sesquiterpenes includes hemi-acetals velutinal (7.12), isovellerol (7.11), rubrocinctal A (7.4), and their derivatives and lactones which are unsubstituted or possess up to three hydroxy groups. Velutinal esters 7.28 and 7.30 have already been illustrated. The free hemiacetal velutinal (7.12) does not occur in intact fruiting bodies where, instead, is contained in the form of esters (see above) however, small amounts of 7.12 were detected by tic in a hexane extract of injured L. vellereus within the first minutes after grinding at 4° (7). Moreover, velutinal could be obtained by ethanolysis at 25° of... 

Oxidative hydroboration 91) of lactone 11.49 afforded a mixture of four lactarorufins (Scheme 20), in which diols 11.30 and 11.33, arising from a attack of diborane, largely predominated (more than 90%). The same type of stereoselectivity was observed for other addition reactions, i.e. epoxidation, osmylation, hydrogenation (775), (704), 43) to 2,9, 3,4- or 6,7-double bond of lactaranolides and marasmanes. Apparently, the tricyclic structures of these substrates provided enough conformational and steric bias to direct approach of reagents from the same side as the bridgehead protons H-2 and H-9. However, when the double bond was located in a different position, exceptions were observed 98). 

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