The stereocontrolled synthesis of phthalic acid 4,5-cis-dihydrodiol. An unambiguous structural assignment of the bacterial metabolite of phthalic acid

Abstract

The stereocontrolled synthesis of the extremely labile phthalic acid 4,5-cis-dihydrodiol(l) has been achieved in a highly efficient manner in seven step from bis[2-(trimenyleiethyl] fumarate (2). The Diela-Alder adduct 3 of the fumarate with furan has been converted into first em-cis-diol 4 and then ita acetonide 5. Treatment of acetonide 5 with lithium hexamethyldisilazide resulta in the regioselective formation of olefinic alcohol 6. Following the introduction of the second double bond into the cyclohexene ring system, the highly sensitive deprotection of the acetonide group of dihydrodiol diester acetonide 7 can be effected under iodine catalysis. The hydrolysis of the 2-(trimethylsily1)ethyl ester group has been achieved by treatment with tetra(n-butyl)ammonium fluoride in THF. This synthesis constitutes an unambiguous assignment of the structure and stereochemistry of the microbial metabolite of phthalic acid. (7) H a " , A.; Alexanian, V. Tetrahedron Lett. 1978,4475.A strategy is described for synthesis of oligomers modified in the 4-position of thymine by postsynthetic substitution. 4-Triamlothymine phoephoramidite monomer has been prepared in one step from thymine amidite monomer and incorporated into a 12 mer AGCGAAXTCGCT using a DNA-synthesizer. The fully protected oligomer containing 4-triazolothymine, while still bound to CPG-support, was treated at 25 "C with either alcohol/DBU, dilute aqueous NaOH, concentrated aqueous ammonia, 1,l-dimethylhydrazine, or thiolacetic acid, to produce essentially pure oligodeoxynucleotides containing @-alkylthymine, thymine, 5-methylcytosine, N4-(dimethylamino)-5-methylcytosine [i.e., 4-(2,2-dimethylhydrazino)-5-methylpyrimid-2-one (TDH)], or 4thiothymine respectively. Thie f i t and efficient synthesis of TDH oligomers indicates that this may be a general route to the synthesis of oligomers containing thymine with a reactive group at the 4-position. The melting temperature (Tm) of a DNA duplex containing TDH:G or TDH:A pairs was similar to that of a duplex with AC mismatch.

Accessing the antipodal series in microbial arene oxidation: a novel diene rearrangement induced by tricarbonyliron(0) complexation

“…The enantiopurity of (2S,3R)-11 was determined to be >95% ee by means of ester reduction and subsequent formation of Mosher's ester derivatives.z Attempted removal of the acetonide in (2S,3R)-11 upon exposure to Brønsted acid proved unsuccessful due to facile dehydration/rearomatisation. However, in preliminary experiments, iodine in methanol 13 has been observed by NMR to afford 12 from (2S,3R)-11, albeit with a degree of concomitant rearomatisation.…”

cis-Tetrahydrofuran-3,4-diol Structure as a Key Skeleton of New Protecting Groups Removable by Self-Cyclization under Oxidative Conditions

“…Because 13 was not easily available, , we designed a new protecting group, CTFOC (Figure ), which could be introduced to the nucleosides as shown in Scheme . Compound 15 was prepared by a Diels−Alder reaction of furan and N -benzylmaleimide. The dihydroxylation , of 15 gave exo - N -(phenylmethyl)-7-oxabicyclo[2.2.1]heptane-5,6-dihydroxy-2,3-dicarboximide ( 16 ) as shown in Scheme .…”

Rhodium(I)-Catalyzed Nucleophilic Ring-Opening Reactions of Oxabicyclo Adducts Derived from the [4 + 2]-Cycloaddition of 2-Imido-Substituted Furans

“…7-Oxabicyclo[2.2.1]heptenes are valuable intermediates in organic synthesis. , The large number of selective transformations possible with the oxabicyclic system endow this nucleus with impressive versatility. − A crucial synthetic transformation employing these intermediates involves the cleavage of the oxygen bridge to produce functionalized cyclohexene derivatives. Many groups have developed different approaches including β-elimination of suitable derivatives, treatment with strong acids, reductive elimination of endo functionalities, fragmentation, hydrolytic ring openings, and alkylative bridge cleavage reactions . A significant advancement in the ring-opening chemistry of oxabicyclic compounds occurred in the early 1990s as a result of the elegant work of Lautens and co-workers .…”