Treatment of 2,,3'-0-methoxyethylideneadenosine (1) with excess pivalic acid chloride in refluxing pyridine gave a mixture composed primarily of 6-lV-pivalamido-9-(3-chloro-3-deoxy-2-0-acetyI-5-0-pivalyl-d-D-xylofuranosyljpurine (2a) and 6-lV-pivalamido-9-(3-chloro-3-deoxy-5-0-pivalyl-2-0-[4,4-dimethyl-3-pivalyloxypent-2enoy 1]-ß-d-xylofuranosyl)purine (2b) in high combined yield. Methanolic sodium methoxide converted this mixture to 9-(2,3-anhydro-/3-D-ribofuranosyl)adenine (adenosine ribo-epoxide) (3) in greater than 60% overall yield from starting adenosine. The epoxide 3 was found to spontaneously decompose (presumably via the N3-*^'xylo-cyclonucleoside, i) to the ring-opened aminoimidazole carboxamidine cyclonucleoside ii in water. Sodium hydroxide smoothly effected transformation of ii to the corresponding carboxamide, iii. Pivalylation and benzoylation of 3 in pyridine with the appropriate acid chloride gave 6-M-pivalamido-9-(5-0-pivalyl-2,3-anhydroß-o -ribofuranosyl)purine ( 4) and the corresponding N,N, 08,-tribenzoate, 6, respectively. Tetraethylammonium fluoride in refluxing acetonitrile followed by methoxide deblocking converted 4 or 6 into 9-(3-fluoro-3-deoxy-/3-D-xylofuranosyl)adenine ( 7). Reaction of 6 with sodium benzoate in moist DMF followed by deblocking gave 9-/3-d -xylofuranosyladenine (adenine xyloside) (8) in high yield. Treatment of 6 with sodium azide in hot DMF gave 9-(3-azido-3-deoxy-/3-n-xylofuranosyl)adenine (9a) in excellent yield after removal of protecting groups. Hydrogenation of 9a gave 9-(3-amino-3-deoxy-/3 -d -xylofuranosyl) adenine (9b). Treatment of the crude product [presumably a mixture of N-benzoylated 9-(3,5-di-0-benzoyl-/3-D-xylofuranosyl)adenines] from sodium benzoate
. Can J. Chem. 55, 1260Chem. 55, (1977. Treatment of the trans iodohydrin acetate, 4-arnino-7-(3-iodo-3-deoxy-2-O-acetyl-5-0-[2,5,5-trimethyl-1,3-dioxolan-4-on-2-yl]-~-~-xylofuranosyl)pyrrolo[2,3-d]pyrimidine (2) with methanolic ammonia gave 2',3'-anhydrotubercidin (3) in 96% yield. N4,N4,05'-Tribenzoylation of 3 gave 4, which is stabilized against intramolecular cyclization. Treatment of 4 with boron trifluoride etherate (3',5'-benzoxonium ion formation) followed by deblocking gave 4-amino-7-B-D-xylofuranosylpyrrolo[2,3-dlpyrimidine (5) in 91% overall yield from tubercidin (1). The 3',5'-0-isopropylidene derivative (6a) of 5 was mesylated to give 6b which was deprotected in acid and the resulting trans hydroxy mesylate was treated with base to give 4-amino-7-(2,3-anhydro-P-D-lyxofuranosyl)pyrrolo[2,3-d]rmdne (7
Ausgehend von Tubercidin (I), dem 7‐Desaza‐Analogen von Adenosin, werden auf dem angegebenen Weg die Derivate mit D‐xylo‐ (IV), d‐lyxo‐(V) und D‐arabino‐Konfiguration (VI) dargestellt.
Der aus Adenosin nach bekannter Methode dargestellte Orthoester (I) gibt bei Reaktion mit Pivalinsäurechlorid als Hauptprodukt ein Gemisch aus der Xylofuranose (IIa) und der Arabinofuranose (IIIa).
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