Building Blocks for the Synthesis of Enantiomerically Pure Jasmonoids: Synthesis of (+)‐Methyl Epijasmonate

Abstract

(equilibrium mixture). Furthermore, l a acts as a pheromone, whereas 1 b is inactive. [,] Finally, cyclopentanes with cis configuration have been shown to be the biogenetic precursors of jasrnon~ids;[~' notably, this also holds true for all reduced compounds such as lactone Zrs1 and cucurbic acid (3),16] neither of which can undergo epimerization at C-2. We have now developed a synthetic strategy that makes avail- Our starting point is the asymmetric Diels-Alder reaction. Several years ago, we found that the uncatalyzed reactions of the fumarates of (8-ethyl lactate and (R)-pantolactone proceed with high diastereosele~tivity.~~~ For example, ester 4, readily available in kilogram quantities, and cyclopentadiene react with a diastereoselectivity of 98:2. The crude product is hydrolyzed with LiOH in THF/water to give the salt of 5-norbornene-2,3-dicarboxylic acid, which is then converted directly, without purification, into the iodolactone 5. Recrystallization affords enantiomerically pure['] 5 in 70-80 Yo yield. Heating a solution of the dried K salt of 5 in dimethyl sulfoxide (DMSO) (9 h, 175 "C) gives lactone 6 in 84% yield.We assume that this new cyclization is a decarboxylative 1,3 elimination. Angen. Chem. h i . Ed. Engl. 29 (1990) No. 9

Jasmonates: key players in the plant defence

“…As a consequence, there have been fewer syntheses of this compound. The first synthesis of enantiomerically pure (+)-(3R,7S)-methyl 7-epijasmonate was presented by Helmchen et al 95 The starting point for this synthesis was an asymmetric Diels-Alder reaction as shown in Scheme 12 using cyclopentadiene as the diene and the fumarate of ethyl (S)lactate, 37, as the chiral dienophile. Hydrolysis of the adduct, followed by cyclisation to the iodolactone afforded enantiomerically pure 96 a synthesis of (+)-methyl 7-epijasmonate from catapol using a variation of their route 93 to ( )-methyl jasmonate shown in Scheme 10 and discussed in section 4.1.…”

Flavours and Fragrances

“…[98] The stereo-differentiating step is a diastereoselective Diels-Alder reaction of cyclopentadiene and diethyl bis-(S)-lactylfumarate. Cleavage of the chiral auxiliary is followed by an iodolactonisation with the endo-carboxylic acid.…”

Lactones in the Synthesis of Prostaglandins and Prostaglandin Analogs

“…The all-cis-Corey lactone 175 , which is a key intermediate in the process for obtaining ent -5-F 2c -IsoP and 5- epi - ent -5-F 2c -IsoP, was synthesized starting from the isomer tricyclic ketone 169 . First, the optically active carboxylic acid 169 was treated with HCl, as for compound 99 , to give 170 at an 82% yield (99% ee ) ( Scheme 35 ) [ 109 , 110 ]. Then, two routes to obtain the chloro δ-lactone 173 were followed.…”