Prenyl esters

Methylbut-2-enyl (Prenyl) Ester (CH3)2C=CHCH202CR Cleavage... 

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. 

Deallylation. The utility of (V-allyloxycarbonyl derivatives in peptide synthesis is demonstrated by deprotection with the Pd-catalyst system in aqueous MeCN. Prenyl esters are not affected during deallylation. 

ZrCLt, NaBH4, CH2CI2, 1.5-4 h, 70-96% yield. Prenyl esters are retained. ... 

Pd(0Ac)2, TPPTS, CH3CN, H2O, EtjNH, 96-100% yield. The allyl carbamate (alloc) group can be cleaved in the presence of the prenyl ester. These conditions will also cleave allyl carbonates, cinnamyl esters, and prenyl carbamates. ... 

There are also excellent total syntheses of spirotryprostatins which do not apply intermolecular functionalisation of the indole 3-position with a C5 prenyl-type precursor and are, therefore, not discussed in detail. Carreira and co-workers started from 3-diazo-2-oxindole, which was used in a Rh(I)-catalysed cyclopropanation of 1,3-pentadiene. The resulting cyclopropane was subjected to Mgl2-catalysed ring expansion and added to an imine affording the spiro[5.5] partial structure [130, 131]. Overman and Rosen built up the indole system by intramolecular Heck reaction of a functionalised iodoaniline [132,133]. In a model study building up the indole system, Cacchi and co-workers synthesised 3-prenylindoles via Pd-catalysed cyclisation of orf/io-alkynyltrifluoroacetanilides with prenyl esters [134]. 

The prenyl (y,y-dimethylaUyl) ester was introduced as a more robust variant of the allyl ester.Experiments have shown that aUyl esters and allyl carbamates can be selectively deprotected in the presence of a prenyl ester,thereby permitting greater precision in the selectivity of deprotection of aUyl-based functionality. 

In addition to the methods described above, prenol (51) can be prepared from methyl-butynol (43) by rearrangement to prenal (52) using a titanium alkoxide/copper chloride catalyst [69, 70] followed by selective hydrogenation using a ruthenium rhodium tris( 7-sulfonatoyl)phosphine trisodium salt (TPPTS) catalyst [71, 72]. However, it is more usual to prepare the prenyl esters by nucleophilic substitution of a carboxylate anion on prenyl chloride [503-60-6] (56) which, in turn, is available through hydrochlorination of isoprene [78-79-5] (1). This hydrochlorination often employs copper ions as catalysts. These processes are shown in Fig. 8.14. 

The formation of IPP proceeds according tg the relatively well established scheme shown in Fig. 1, ultimately from acetyl-CoA. There are three sites or compartments in the plant cell lAihere prenyllipids are synthesized (i) the endoplasmic reticulum (ER) for sterol formation (ii) the piastids for the synthesis of the side chains of chlorophylls, quinones and tocopherols, and of the carotenoids and fatty acid prenyl esters (iii) the mitochondria for the synthesis of the ubiquinone side chains. Therefore, the question arises whether there are also three cellular sites for IPP formation, whereby the cytopiasm/ER is uncontested. ... 

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. 

PoIy(styrene-co-maleic aci partial propyl ester Maleic anhydride-styrene polymer, propyl ester 68890-81-3 2,5-Furandione, polymer with ethenylben2 e, prenyl ester R Unk... 

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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