Carboxylic acids prenyl esters

The cinnamyl ester can be prepared from an activated carboxylic acid derivative and cinnamyl alcohol or by transesterification with cinnamyl alcohol in the presence of the H-Beta Zeolite (toluene, reflux, 8 h, 59-96% yield). It is cleaved under nearly neutral conditions [Hg(OAc)2, MeOH, 23°, 2-A h KSCN, H2O, 23°, 12-16 h, 90% yield]or by treatment with Sulfated-Sn02, toluene, anisole, reflux. The latter conditions also cleave crotyl and prenyl esters. 

Preparation of (5)-6-bromo-8-(3-prenyl)-3a-(3-oxo-propyl)-3,3a,8,8a-tetrahydro-2//-pyrrolo[2,3-6)indole-l-carboxylic acid tert-butyl ester (222) from A -lO-BOC-l-prenyl-6-bromotryptamine (220), acrolein (213), and MacMillan catalyst 211A... 

Deprotection of prenyl esters to carboxylic acids is successfully achieved by using a catalytic amount of (la) [156]. This method is tolerant to various functionalities such as protected a-amino groups, other esters, and carbon-carbon multiple bonds. 

Regioselective hydroacyloxylation of l,l-dimethylaUene with carboxylic acids exploiting iridium catalyst to prenyl ester was reported in 74—82% isolated yield [59] (Scheme 36). 

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