A new straightforward method of synthesis of dendrimers, using two branched monomers (CA(2) and DB(2)), is described. Each generation is obtained in a single quantitative step, with only N(2) or H(2)O as byproducts; generation 4 is obtained in only four steps. The end groups are alternatively phosphines and hydrazines; their versatile reactivity is illustrated by the reaction of generation 4 with a branched CD(5) monomer, which increases the number of end groups in a single step from 48 to 250.

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The crystal and molecular structure of diastereomerically pure N 4-benzoyl-2‘-deoxycytidine 3‘-O-(Se-methyl methanephosphonoselenolate (FAST-eluted) (4, R = H, B = CBz) and 5‘-O-pixylthymidine 3‘-O-(S-methyl methanephosphonothiolate (FAST-eluted) (5) have been elucidated by X-ray crystallography. The absolute configuration at the phosphorus atom in both compounds is S P. Each FAST-4‘ (R = DMT, B = CBz) and FAST-5 (R = Px, B = Thy) in the process of DBU/LiCl-assisted condensation with 3‘-O-acetyl-N 4-benzoylcytidine and 3‘-O-acetylthymidine gave after deprotection (S P)-dicytidine-(3‘,5‘)-methanephosphonate and (S P)- dithymidine-(3‘,5‘)-methanephosphonate, respectively. Unambiguous assignment of the absolute configuration at the phosphorus in 4 (R = H, B = CBz) and 5 (R = Px, B = Thy) allows for stereochemical correlation and the conclusion that DBU/LiCl-assisted nucleophilic substitution at phosphorus occurs with net inversion of configuration, in contrast to our earlier erroneous deduction. Moreover, the knowledge of the absolute configuration at the phosphorus atom in both 4 (R = H, B = C Bz ) and 5 (R = Px, B = Thy) allows for assignment of the absolute configuration at phosphorus in precursors of 4‘ and 5, such as 5‘-O-DMT-nucleoside 3‘-O- methanephosphonothioanilidates (6), methanephosphonoanilidates (8), and methanephosphonoselenoanilidates (9).

[formula: see text] A method for a large-scale synthesis of stereodefined oligo(nucleoside 3',5'-methanephosphonates) has been developed, based on transient 3'-O protection, which allows for the conversion of the protecting chirally defined methanephosphonanilidate group, located at the 3' end of a stereoregular oligomer, into diastereomerically pure "oligomeric building blocks" for stereospecific coupling with the 5'-OH group of another oligonucleotide.

New Stereospecific Method of Synthesis of (Sp)-and (Rp)-Dinucleoside-( 3',5') Methanephosphonates. -Diastereomerically pure dinucleoside 3',5"-methanephosphonates and all-Rp or all-Sp trimers, tetramers or pentamers are prepared by a stereoselective condensation of diastereomerically pure nucleoside 5'-O-(4,4-dimethoxytrityl) 3'-O-(Se-methyl methanephosphonoselenolates) and 3'-O-acetyl nucleosides in the presence of DBU/LiCl. -(WOZNIAK, L. A.; PYZOWSKI, J.; WIECZOREK, M.; STEC, W.

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

No abstract