Those skilled in the art will appreciate that numerous changes and modifications may be made to the preferred embodiments of the present invention and that such changes and modifications may be made without departing from the spirit of the invention. It is therefore intended that the appended claims cover all such equivalent variations as fall within the spirit and scope of the invention. 

Notably, throughout this application various citations are provided. Each citation is specifically incorporated herein by reference in its entirety. 

Those skilled in the art will appreciate that numerous changes and modifications may be made to the preferred embodiments of the invention and that such changes and modifications may be made without departing from the spirit of the invention. It is therefore intended that the appended 15 claims cover all such equivalent variations as fall within the true spirit and scope of the invention. 

What is claimed is: 

1. A method for the solid phase synthesis of oligonucle› otides, wherein each synthesis cycle of the method com- prises: 

a) cleaving an acyl front end protective group from a nucleoside immobilized on a solid support to liberate a hydroxyl group on the nucleoside, the acyl front end protective group comprising either an electron with› drawing group or a group capable of neighboring group participation in close proximity to its carbonyl group such that the acyl group is cleavable in ten minutes or less at room temperature by a primary amine, a second› ary amine, or a mixture thereof; and 

b) coupling an acyl protected nucleoside phosphoramidite with the hydroxyl group of the nucleoside immobilized on the solid support. 

2. The method of claim 1, wherein the acyl protective group is selected from the group consisting of an oxalyl monoester group, an ortho-phenoxycarbonyl benzoyl group, and a cyclohexyloxydicarbonyl group. 

3. The method of claim 2, wherein the ortho-phenoxycar› bonyl benzoyl group is selected from the group consisting of a 2-(4-nitrophenoxy)carbonyl benzoyl group and a 2-(2-cy- anophenoxy)carbonyl benzoyl group. 

4. The method of claim 1, wherein the acyl protective group is attached to the 5’-hydroxyl function of the nucleoside. 

5. The method of claim 1, wherein the acyl protective group is attached to the 3’-hydroxyl function of the nucleoside. 

6. The method of claim 1, wherein the cleaving reagent comprises a primary amine. 

7. The method of claim 6, wherein the primary amine is selected from the group consisting ofn-butylamine, n-hexy› lamine, 2-methoxyethylamine, and 2-(N,N-diethylamino) ethylamine. 

8. The method of claim 1, wherein the cleavage of the front end protective group occurs in 1 minute or less at room temperature. 

9. The method of claim 1, wherein the first nucleoside of the oligonucleotide to be synthesized is attached to the solid support via an acid-labile linker. 

10. The method of claim 1, wherein the base moiety of the nucleoside phosphoramidite is either unprotected or pro› tected with an acid-labile nucleobase protective group. 

11. The method of claim 10, wherein, after synthesis of the oligonucleotide, the nucleobase protective groups of the oli› gonucleotide are removed with an acidic reagent. 

12. The method of claim 11, wherein the acidic reagent is aqueous. 

13. The method of claim 12, wherein the aqueous acidic reagent has a pH in the range of pH 2 to pH 4. 

14. The method of claim 1, wherein the nucleoside phos› phoramidite is a ribonucleoside and the 2’-hydroxyl function of the ribonucleoside is protected with an acid-labile 2’-pro› tective group. 

15. Anucleoside phosphoramidite comprising an acyl front end protective group and a phosphoramidite group, wherein the acyl front end protective group comprises either an elec› tron withdrawing group or a group capable of neighboring group participation in close proximity to its carbonyl group such that the acyl group is cleavable with a primary amine, a secondary amine, or a mixture thereof in 10 minutes or less at room temperature. 

16. The nucleoside phosphoramidite of claim 15, wherein the acyl front end protective group is an oxalyl monoester group. 

17. The nucleoside phosphoramidite of claim 15, wherein the acyl front end protective group is an ortho-phenoxycar› bonyl benzoylgroup. 

18. The nucleoside phosphoramidite of claim 17, wherein the ortho-phenoxycarbonyl benzoyl group is selected from the group consisting of a 2-(4-nitrophenoxy)carbonyl ben- zoyl group and a 2-(2-cyanophenoxy)carbonyl benzoyl group. 

19. The nucleoside phosphoramidite of claim 15, wherein the acyl front end protective group is a cyclohexyloxydicar› bonyl group. 

20. The nucleoside phosphoramidite of claim 15, wherein the phosphoramidite group comprises a ~-cyanoethyl phos› phate protective group. 

21. The nucleoside phosphoramidite of claim 15, wherein the base moiety of the nucleoside phosphoramidite is pro- tected with an acid-labile nucleobase protective group. 

22. The nucleoside phosphoramidite of claim 15, wherein the nucleoside is a ribonucleoside and the 2’-hydroxyl func› tion of the ribonucleoside is protected with an acid-labile 2’-protective group. 

23. The nucleoside phosphoramidite of claim 22, wherein the acid-labile 2’-protective group a 4-methoxytetrahydro› pyranyl group. 

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