References:

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[1]Ashton, W.T., Karkas, J.D., Field, A.K., Tolman, R.L., 1982. Activation by thymidine kinase and potent antiherpetic activity of 2’-nor-2’-deoxyguanosine (2’NDG). Biochemical and Biophysical Research Communications, 108(4):1716-1721.

[2]Brand, B., Reese, C.B., Song, Q., Visintin, C., 1999. Convenient syntheses of 9-[4-hydroxy-3-(hydroxymethyl)butyl] guanine (penciclovir) and 9-[4-acetoxy-3-(acetoxymethyl) butyl]-2-amino-9H-purine (famciclovir). Tetrahedron, 55(16):5239-5252.

[3]De Clercq, E., 1991. Broad-spectrum anti-DNA virus and anti- retrovirus activity of phosphonylmethoxyalkylpurines and pyrimidines. Biochemical Pharmacology, 42(5):963-972.

[4]Dey, S., Garner, P., 2000. Synthesis of tert-butoxycarbonyl (Boc)-protected purines. The Journal of Organic Chemistry, 65(22):7697-7699.

[5]Geen, G.R., Grinter, T.J., Kincey, P.M., Jarvest, R.L., 1990. The effect of the C-6 substituent on the regioselectivity of N-alkylation of 2-aminopurines. Tetrahedron, 46(19):6903-6914.

[6]Geen, G.R., Kincey, P.M., Choudary, B.M., 1992. Regiospecific Michael additions with 2-aminopurines. Tetrahedron Letters, 33(32):4609-4612.

[7]Harnden, M.R., Jarvest, R.L., 1985. An improved synthesis of the antiviral acyclonucleoside 9-(4-hydroxy-3-hydroxymethylbut-1-yl) guanine. Tetrahedron Letters, 26(35):4265-4268.

[8]Harnden, M.R., Jarvest, R.L., Bacon, T.H., Boyd, M.R., 1987. Synthesis and antiviral activity of 9-[4-hydroxy-3- (hydroxymethyl) but-1-yl] purines. Journal of Medicinal Chemistry, 30(9):1636-1642.

[9]Hwu, J.R., Jain, M.L., Tsay, S.C., Hakimelahi, G.H., 1996. Ceric ammonium nitrate in the deprotection of tert- butoxycarbonyl group. Tetrahedron Letters, 37(12):2035- 2038.

[10]Kim, D.K., Lee, N., Kim, Y.W., Chang, K.Y., Kim, J.S., Im, G.J., Choi, W.S., Jung, I.H., Kim, T.S., Hwang, Y.Y., 1998. Synthesis and evaluation of 2-amino-9-(3-hydroxymethyl- 4-alkoxycarbonylo-xybut-1-yl) purines as potential prodrugs of penciclovir. Journal of Medicinal Chemistry, 41(18):3435-3441.

[11]Kitade, Y., Ando, T., Yamaguchi, T., Hori, A., Nakanishi, M., Ueno, Y., 2006. 4’-fluorinated carbocyclic nucleosides: synthesis and inhibitory activity against S-adenosyl-l- homocysteine hydrolase. Bioorganic & Medicinal Chemistry, 14(16):5578-5583.

[12]Korba, B.E., Boyd, M.R., 1996. Penciclovir is a selective inhibitor of hepatitis B virus replication in cultured human hepatoblastoma cells. Antimicrobial Agents and Chemotherapy, 40(13):1282-1284.

[13]Lu, W., Sengupta, S., Petersen, J.L., Akhmedov, N.G., Shi, X., 2007. Mitsunobu coupling of nucleobases and alcohols: an efficient, practical synthesis for novel nonsugar carbon nucleosides. Journal of Organic Chemistry, 72(13):5012- 5015.

[14]Martin, J.C., Dvorak, C.A., Smee, D.F., Matthews, T.R., Verheyden, J.P.H., 1983. 9-(1,3-dihydroxy-2-propoxymethyl) guanine: a new potent and selective antiherpes agent. Journal of Medicinal Chemistry, 26(5):759-761.

[15]Mitsunobu, O., 1981. The use of diethyl azodicarboxylate and triphenylphosphine in synthesis and transformation of natural products. Synthesis, 1981(1):1-28.

[16]Ogilvie, K.K., Cheriyan, U.O., Radatus, B.K., Smith, K.O., Galloway, K.S., Kennell, W.L., 1982. Biologically active acyclonucleoside analogues. II. The synthesis of 9-[[2- hydroxy-1-(hydroxymethyl)ethoxy]methyl] guanine (BIOLF-62). Canadian Journal of Chemistry, 60(24):3005-3010.

[17]Porcheddu, A., Giacomelli, G., Piredda, I., Carta, M., Nieddu, G., 2008. A Practical and efficient approach to PNA monomers compatible with Fmoc-mediated solid-phase synthesis protocols. European Journal of Organic Chemistry, 2008(34):5786-5797.

[18]Schaeffer, H.J., Beauchamp, L., Miranda, P.D., Elion, G.B., Bauer, D.J., Collins, P., 1978. 9-(2-hydroxyethoxymethyl) guanine activity against viruses of the herpes group. Nature, 272(5654):583-585.

[19]Shaw, T., Amor, P., Civitico, G., Boyd, M., Locarnini, S., 1994. In vitro antiviral activity of penciclovir, a novel purine nucleoside, against duck hepatitis B virus. Antimicrobial Agents and Chemotherapy, 38(4):719-723.

[20]Smith, K.O., Galloway, K.S., Kennell, W.L., Ogilvie, K.K., Radatus, B.K., 1982. A new nucleoside analog, 9-[[2- hydroxy-1-(hydroxymethyl)ethoxyl]methyl] guanine, highly active in vitro against herpes simplex virus types 1 and 2. Antimicrobial Agents and Chemotherapy, 22(1):55-61.

[21]Tippie, M.A., Martin, J.C., Smee, D.F., Matthews, T.R., Verheyden, J.P.M., 1984. Antiherpes simplex virus activity of 9-[4-hydroxy-3-(hydroxymethyl)-1-butyl] guanine. Nucleosides and Nucleotides, 3(5):525-535.

[22]Toyokuni, T., Walsh, J.C., Namavari, M., Shinde, S.S., Moore, J.R., Barrio, J.R., Satyamurthy, N., 2003. Selective and practical synthesis of penciclovir. Synthetic Communications, 33(22):3897-3905.

[23]Sikchi, S.A., Hultin, P.G., 2006. Solventless protocol for efficient Bis-N-Boc protection of adenosine, cytidine, and guanosine derivatives. Journal of Organic Chemistry, 71(16):5888-5891.

[24]Siro, J.G., Martin, J., Garcia-Navio, J.L., Remuinan, M.J., Vaquero, J.J., 1998. Easy microwave assisted deprotection of N-Boc derivatives. Synlett, 1998(2):147-148.

[25]Swamy, K.C.K., Kumar, N.N.B., Balaraman, E., Kumar, K.V.P.P., 2009. Mitsunobu and related reactions: advances and applications. Chemical Reviews, 109(6):2551-2651.

[26]Wang, L., Dai, L.Y., Lei, M., Chen, Y., 2008. Solubility of hexamethylenetetramine in a pure water, methanol, acetic acid, and ethanol+water mixture from (299.38 to 340.35) K. Journal of Chemical & Engineering Data, 53(12):2907-2909.

[27]Yang, J., Dai, L., Wang, X., Chen, Y., 2011. Di-p-nitrobenzyl azodicarboxylate (DNAD): an alternative azo-reagent for the Mitsunobu reaction. Tetrahedron, 67(7):1456-1462.

[28]Yang, M.M., Schneller, S.W., Korba, B., 2005. 5’-homoneplanocin a inhibits hepatitis B and hepatitis C. Journal of Medicinal Chemistry, 48(15):5043-5046.

[29]Yin, X.Q., Li, W.K., Schneller, S.W., 2006. An efficient Mitsunobu coupling to adenine-derived carbocyclic nucleosides. Tetrahedron Letters, 47(52):9187-9189.

[30]Zheng, Q.H., Wang, J.Q., Liu, X., Fei, X.S., Mock, B.H., Glick-Wilson, B.E., Sullivan, M.L., Raikwar, S.P., Gardner, T.A., Kao, C.H., et al., 2004. An improved total synthesis of PET HSV-tk gene reporter probe 9-(4-[¹⁸F] fluoro-3-hydroxymethylbutyl) guanine ([¹⁸F]FHBG). Synthetic Communications, 34(4):689-704.