The Synthesis of Nucleoside and Nucleotide Analogs Derived from Uridine^*

Intramolecular Michael Additions in Uridine Derivatives: Isolation of the Labile 5′O-C6 Cyclonucleoside

“…The cyclization reaction is indeed reversible in basic conditions for all the three cyclonucleosides studied (results not shown) in agreement with the reported literature for N -cyclonucleoside 2a ( 17 ) and S -cyclonucleoside 3a . 15 , 16 For instance, the O -cyclonucleoside 1 was converted back to 4 in a few minutes at pH 13 (TLC monitoring). With the noticeable exception of the N -cyclonucleoside 2a (that possesses a basic character prone to promote the retro-Michael reaction), the other cyclonucleosides are quite stable in acidic conditions, although the hydrolysis of the ketal is observed at pH < 2.…”

Study of the pyrimidine nucleobase C5C6 bond reactivity under thio‐michael/aldol tandem reaction conditions

“…To a solution of 2 [8] (100 mg, 0.3 mmol) in MeOH (1 mL) were added benzaldehyde (0.3 ml, 3 mmol) then a saturated methanolic K 2 CO 3 solution (2 mL). The reaction was stirred at room temperature for 3 h then poured dropwise in a saturated aqueous NH 4 Cl solution (3 mL).…”

“…The required thiolate 1a was generated in situ by alkaline hydrolysis of 2 since 1a spontaneously leads to its isomeric cyclic sulfide form 1b [8]. Treatment of 2 in methanol and in the presence of K 2 CO 3 with benzaldehyde (10 equiv) at room temperature under an argon atmosphere afforded 3 in 79% together with the disulfide derivative 4 in 10%.…”

Synthesis and Reaction of Pyrimidine Nucleosides

“…(680) The reaction of sufur nueleophiles with 5'-deoxy-5'-iodo-2',3'-0-isopropylideneuridine gave the 5' -methylthio, (259) 5' -thioacetyl, (259.681) 5' -mercapto, and 5' -thiocyanato derivatives. (259) The 5' -mercapto derivatives of 2' -deoxyuridine and its 5-fluoro derivatives have also been prepared. (261).…”