1. Synthesis of five-MemberedConformationally Locked 2´,4´-Carbocyclic ribo- Thimidine. Khobragade Premkumar Anandrao Chembiotek, Hinjewadi, Pune

2. Antisense therapeutic agent.

3. Reagents and conditions: (i)Acetone, sulphuric acid, rt, overnight. (ii)Oxalyl chloride, DMSO,, -78 °C, DIPEA, DCM. 95% 65%

4. 62% 75% Reagents and conditions: (i)Sodium Borohydride, EtOH, rt, 2 hr, (ii)NaH, BnBr, -5 °C to rt overnight.

5. 65% Reagents and conditions: (i)80% AcOH, rt, overnight, (ii)Sodium metaperiodate, THF, Water, rt, 4 hr.

6. Reagents and conditions: (i)NaOH, formalin, rt, overnight; (ii)NaH, BnBr, -5 °C to rt, 4 hr. 63%66%

7. Reagents and conditions: (i) Oxalyl chloride, DMSO, -78 °C, DIPEA, DCM, (ii) PPh3+CH3Br-, 1.6 M butyllithium in hexane, THF, -78 °C to rt overnight. 87%

8. Reagents and conditions:80% (i) 9-BBN, THF, 3 N NaOH, 33% H2O2, (ii) Oxalyl chloride, DMSO, -78 °C, DIPEA, DCM, PPh 3+CH3Br-, 1.6 M butyllithium in hexane, THF, -78 °C to rt overnight. 95% 70%

9. Reagents and conditions: (i)Acetic acid, acetic anhydride, triflic acid, rt, 30 min. (ii)persilylated thymine, TMSOTf, CH3CN, 0 °C to rt, overnight. 80%

10. Reagents and conditions: (i)27% methanolic NH3,rt, overnight, (ii)DMAP, phenyl chlorothionoformate, pyridine,rt, overnight. 72%

11. Reagents and conditions: (i)Bu3SnH, toluene, AIBN, 4 h, (ii)20% Pd(OH)2/ C, Ammonium Formate, Methanol, Reflux, 8 h. 73% 76%

12. Reagents and conditions: (i)DMTr-Cl, Pyridine, Overnight, (ii)2-cyanoethyl N,N-diisopropylphosphoramidochloridite, DIPEA, dry THF, overnight. 74% 80%

13. Thank you.