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A study concerning the synthesis of the scopadulan diterpenes is presented. The use of (+)-podocarp-8(14)-en-13-one as starting material is discussed.

A method for the selective deprotection of acetates was developed based on the utilization of magnesium methoxide as an selective reagent. The primary acetates were effectively differentiated by adjusting the equivalents of the magnesium methoxide reagent. The mild reagent selectively cleaved the primary acetate from the secondary acetates and tertiary acetates with different steric environments. The reagent for selective deacylation reaction exhibited high selectivity in ester deprotection.

The effect of solvent on the alpha-effect nucleophiles was investigated through nucleophilic substitution reactions of p-nitrophenyl acetate (PNPA) with m-chlorophenoxide (ClPhO-) and benzohydroxamates (BHA-). Kinetic studies and relative basicity measurements revealed that MeCN addition determined the decreasing alpha-effect trend shown by BHA- and MBHA-. The decrease in the alpha-effect resulted in an equilibrium shift of hydroxamates (I) toward their isomeric structures.

The mechanism of aminolysis phenyl dithioacetates in acetonitrile was investigated through probing the effects of the substituents in the nucleophile and leaving group. It was shown that the mechanism was an uncomplicated one involving only one tetrahedral intermediate. The fast proton transfer step was rate-determining in the aminolysis of thiono and dithiono esters and carbonates.

A series of 4,4-disubstituted gamma-lactone products was synthesized based on a method involving sequential Rh(II)-catalyzed reactions. The synthetic process was characterized by the use of Rh2(OAv)4 as catalysts for tertiary C-H insertions and cyclopropanation. The ester-substituted Rh(II) carbenoids were also responsive to the electronic nature of the ligand on the dirhodium(II) metal. Furthermore, the nature of the alkyl moiety in the alpha-(alkoxycarbonyl) substituent did not affect the regioselectivity of the reaction.

A method for the stereoselective synthesis of Z-unsaturated esters was developed by utilizing novel ethyl(diarylphosphono)acetates that were generated from triethyl phosphonoacetate, PCl5 and phenols. The novel Horner-Emmons reagents reacted with benzyltrimethylammonium hydroxide and benzaldehyde in tetrahydrofuran to produce a Z-isomer in 98% chemical yield. The reaction of the novel Horner-Emmons reagents with trans-2-hexenal also improved Z-selectivity.

A novel method for the synthesis of 2-[(trimethylsilyl)methyl]-2-propen-1-yl acetate was developed based on transition-metal-promoted reactions. The synthetic strategy involved a Diels-Alder/electrophilic substitution sequence that led to the Ni-catalyzed cross-coupling of vinyl halide compounds containing alcohol moieties with Grignard reagents. The synthetic process also involved the deprotonation of alcohol with n-butyllithium to produced 2-[(trimethylsilyl)methyl]-2-propen-1-yl acetate.

A method for the selective deprotection of acetates was developed based on the utilization of magnesium methoxide as an selective reagent. The primary acetates were effectively differentiated by adjusting the equivalents of the magnesium methoxide reagent. The mild reagent selectively cleaved the primary acetate from the secondary acetates and tertiary acetates with different steric environments. The reagent for selective deacylation reaction exhibited high selectivity in ester deprotection.

Membrane introduction mass spectrometry (MIMS) is shown to be capable of performing on-line monitoring of photolysis reactions. Such capability is then used to monitor the products of photolysis of benzyl acetate in aqueous methanol and 3,5-dimethoxybenzyl acetate in water. Three products, namely, benzyl methyl ester, ethylbenzene and bibenzyl, are noted in the benzyl acetate photolysis, while two products, 3,5-dimethoxybenzyl alcohol and 3,5-dimethoxyethylbenzene, are observed in the photolysis of 3,5-dimethoxybenzyl acetate. Findings show that the solvent and the photon intensity determine the reaction rates. They also affirm that photolysis proceeds through both ion and radical pair intermediates.

A new pathway to functionalized juglones, which is derived from condensative and intramolecular acylation techniques, involved the retrosynthetic preparation of the desired juglone moiety through the demethylation/oxidation of 1,4-dimethoxynapthalene derivatives. An adduct, appropriate for straightforward thermolysis to a methoxy ester, resulted from the reaction of chlorojuglone with 1-methoxy-1, 3-cyclohexadiene (II), in the preparation of rhein. Aloe emodin derivative resulted from the conversion of juglone acetate.

Approximately 90% of the isomer of a bicyclo-(3.2.1) with 56% of (+)-podocarpic acid precusor with 82% de resulted from Mn-based oxidative free-radical cyclization of phenylmenthyl esters. De in the two esters exhibited different orientation. The size of the alpha-substituent and double-bound substitution pattern influenced the degree and orientation of de.

The South Pacific mollusc Onchidium sp. yields onchitriols I A-D and II A-D, each bearing two gamma-pyrones within a 19-membered 6,15-dioxoalken-9-yl chain. Spectroscopic studies establish their molecular formulas as C36H52O2 (IA), C37H54O9 (IB and IC, isomers at C-11/C-13), C40H58O10 (ID), C34H50O8 (IIA), C35H52O8 (IIB), C38H54O10 (IIC) and C36H52O9 (IID). On saponification, I A-D yields the deesterified onchitriol I (C32H48O7)while II A-D yield the deesterified onchitriol II (C32H48O7). Trost-Mosher mandelation sets the absolute configuration of onchitriol I as 3S,4S,10S,13R,14R,15R,16R and that of onchitriol II as 3S,4S,10R,13S,14R,15R,16R.

A feasible stereoselective synthesis of alpha-hydroxy-alpha-phenyl-alpa-(1-propyn-3-yl)acetic acid in high enantiomeric excess was developed. The synthesis also allows determination of the (R/S) conformation at the acetate center. The assignment of (E)-(R,R)-IQNP as the isomer demonstrating binding to the M1 muscarinic acetyl-choline receptor (mAChR) subtype and (Z)-(R,R)-IQNP as the isomer binding to both the M1 and M2 mAChR subtypes was gleaned from a comparison of the specific rotation, high performance liquid chromatography and nuclear magnetic resonance data of (E)-(R,R)- and (E)-(R,S)-IQNP to those generated by a classical resolution of the acetate moiety.

Unsymmetrical disubstituted vic-diols react with trimethyl orthoacetate in the presence of TsOH in CH2Cl2 to form monoacetates. The reaction has a good regioselectivity due to the acidic hydroxy groups and steric interactions. The acetyl groups are preferentially attached to the hydroxyls on less substituted carbon atoms. The reaction involves the formation of cyclic orthoesters as intermediates. There is no correlation between the stereochemistry of the orthoesters and the monoacetates. Less reactive diols react with trimethyl orthoformate to form the monoacetates.

Palladium(0) catalyzes the coupling reaction between diethyl N-sodio-N(tert-butoxycarbonyl)phosphoramide and allylic acetates to produce N-protected allylic amines. Mildness conditions associated with selective deprotection enable this method to produce primary and secondary allylic amines. Various substituted allylic acetates give lower yields and require larger reaction times.

The 1,1-diacetates or acylals are commonly utilized as aldehyde protecting groups instead of acetals. The acylals are synthesized by the reaction of simple and hydrides with aldehydes in the presence of sulfuric acid, phosphoric acid and methane-sulfonic acid. However, ZnCl2, FeCl3 and zeolites can also be utilized as catalysts for the conversion of aldehydes to acylals. High yields of the desired product was also synthesized from aromatic or aliphatic aldehydes and alpha, beta-unsaturated ones with iodine as catalyst.

The first intramolecular version of the Pd(O)-catalyzed reaction of 2,7,8-octatrienyl acetates and 1-vinyl-4,5-hexadienyl acetates, where the allene and the pi-allylpalladium unit are fastened by two and three carbon chains, is presented. Two modes of cyclization were derived from the novel intramolecular reactions of the pi-allylpalladium intermediates to allene moieties. These two approaches are effective for construction of carbocycles by tandem reactions.

Receptor binding is independent of the acetate group at C-10 of taxol, the anticancer agent. A deoxygenated taxol analog and its congener, 7-deoxytaxol and 7,10-dideoxytaxol, are prepared and characterized. Antitumor activity does not require the presence of the C-7 hydroxyl group. Xanthane in one of its various forms is produced in small quantities when carbondisulfide and sodium hydride in THF are added to baccatin. Hydrocarbon solvents are ineffective in dissolving the xanthane compound, which is deoxygenated after silylation at C-13.