Thermolytic carbonates for potential 5'-hydroxyl protection of deoxyribonucleosides.
Thermolytic groups structurally related to well-studied heat-sensitive phosphate/thiophosphate protecting groups have been evaluated for 5'-hydroxyl protection of deoxyribonucleosides as carbonates and for potential use in solid-phase oligonucleotide synthesis. The spatial arrangement of selected functional groups forming an asymmetric nucleosidic 5'-O-carbonic acid ester has been designed to enable heat-induced cyclodecarbonation reactions, which would result in the release of carbon dioxide and the generation of a nucleosidic 5'-hydroxyl group. The nucleosidic 5'-O-carbonates 3-8, 10-15, and 19-21 were prepared and were isolated in yields ranging from 45 to 83%. Thermolytic deprotection of these carbonates is preferably performed in aqueous organic solvent at 90 degrees C under near neutral conditions. The rates of carbonate deprotection are dependent on the nucleophilicity of the functional group involved in the postulated cyclodecarbonation reaction and on solvent polarity. Deprotection kinetics increase according to the following order: 4 < 5 < 10 < 6 < 12 < 7 < 13 < 8 < 14 congruent with 19-21 and CCl4 < dioxane < MeCN < t-BuOH < MeCN:phosphate buffer (3:1 v/v, pH 7.0) < EtOH:phosphate buffer (1:1 v/v, pH 7.0). Complete thermolytic deprotection of carbonates 7, 8, 13, and 14 is achieved within 20 min to 2 h under optimal conditions in phosphate buffer-MeCN. The 2-(2-pyridyl)amino-1-phenylethyl and 2-[N-methyl-N-(2-pyridyl)]aminoethyl groups are particularly promising for 5'-hydroxyl protection of deoxyribonucleosides as thermolytic carbonates.
Chmielewski
Marcin K
MK
Division of Therapeutic Proteins, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USA.
Marchán
Vicente
V
Cieślak
Jacek
J
Grajkowski
Andrzej
A
Livengood
Victor
V
Münch
Ursula
U
Wilk
Andrzej
A
Beaucage
Serge L
SL
D002254:Carbonates / Q000737:chemistry*; D003500:Cyclization; D003853:Deoxyribonucleosides / Q000737:chemistry*; D006358:Hot Temperature; D006900:Hydroxylation; D013237:Stereoisomerism; D013942:Thymine Nucleotides / Q000737:chemistry
D002254:Carbonates; D003853:Deoxyribonucleosides; D013942:Thymine Nucleotides