Synthesis and conformational studies of phosphate esters of 1,2-O-isopropylidene-α-D-ribo- and xylo- pentofuranoses

Abstract

. J . Chem. 61, 1387 (1983).The synthcsis and properties. particularly ' H , "P, and ' " nmr, of new phosphate estcrs of I ,2-0-isopropylidene-a-D-riboand xylo-furanoses arc described. For the cyclic phosphates the configuration at the asymmetric phosphorus atom is determined and for all derivatives the preferred conformation of the furanosc and dioxaphosphorinanc rings and the conformation around the phosphoester bonds are prcscnted. Thc dependency of 'Jr>occ coupling constants on factors other than dihcdral angles is reportcd and discussed.JEAN-RICHARD NEESER, JEAN M . J . TRONCHET ct ETIENNE J . CHAROLLAIS. Can. J . Chem. 61, 1387 (1983). Nous dCcrivons la synthhsc ct les proprietes spectroscopiques (en particulier de rmn ' H , "P ct "C) de nouveaux esters phosphoriques de 0-isopropylidkne-1 ,2-u-D-ribo-et xylo-furannoses. Pour les dCrivCs phosphatc cyclique, la configuration au nivcau de I'atome dc phosphore asyrnetriquc a CtC attribuCe, et pour tous nos composCs, la conformation prCfCrenticlle des cycles furannosique et dioxaphosphorinanne, ainsi que la conformation autour des liaisons phosphoester, sont dCterminCcs. Nous observons Cgalcment une variation des constantes dc couplage Ilr,occ en fonction d'autres facteurs quc les angles dikdres et discutons de la signification de tcls resultats.Considering the importance of pentose phosphates, either by themselves, as structural units of nucleotides, or in metabolic biochemical systems, we were prompted to study derivatives of two important naturally occurring pentoses, namely D-xylose and D-ribose. The observations made on these model compounds might prove useful in the understanding of the conformational properties of biologically important nucleotide derivatives.Syntheses of derivatives 1 to 12 were carried out from 1 ,2-0-isopropylidene-a-D-xylofuranose (A) or 1,2-0-isopropylidene-a-D-ribofuranose (B), as depicted in Fig. 1.Results and discussion 1. Itflared ntzd n~icle~zr magnetic resotzntzce spectroscopy.Conji:guratiot~al assigr~met~t of asjltntnetrical phosphorus atoms in compounds 1 to 4 As previously reported (6-9), the values of the P=O stretching frequency (around 1300 cm-') can be used successfully to assign the configuration of phosphorus atoms of a pair of asymmetrical phosphorus-containing epimeric dioxaphosphorinane rings. Such an assignment is dependent on the orientation of the P=O bond, resulting from the conformation of the heterocycles. For example, in compound 1: v P=O (equatorial) = 1295 cm-', and in compound 2: v P=O (axial) = 1285 cm-'.Tables 1-4 summarize the nrnr data for compounds 1 to 12. As previously reported (7-9), "P chemical shifts of derivatives 1 and 2 show a dependence similar to that of v P=O, as a function of the orientation of the phosphoryl bond: in compound 1, 6 "P = + 16.80 ( P = 0 equatorial) and in compound 2, 6 "P = + 14.10 (P=O axial). Configurational assignment of the phosphorus atom for 3 was deduced from a comparison of the 'H and "C nrnr spectra of 1 and 3. The phosphorus atom configuration for 4 was establish...

Structural analysis of 3-C-phosphonates, -phosphinates, and -phosphine oxides of branched-chain sugars

“…(C) Confortnational assigr~ment of the oxnphospholanefuranose bicyclic systerlz for derivatives 9 to 12 Use of 'J coupling constants for conformational analysis requires careful selection of the constants and of the 3J VS. 0 correlation equations. Many authors have previously proposed correlation equations related to such proton-proton and proton-phosphorus couplings for various 1,2-0-isopropylidene-furanose derivatives (9), sugar-phosphates (1,25), or phosphonate derivatives (see eq.…”

6-Membered P-Heterocycles: Ring-Condensed 1,3,2-Diheterophosphorinane 2-Chalcogenides

“…However, on the basis of 1 H NMR measurements the existence of C 2 was excluded for both P epimers of 2-oxo-and 2-thio-1,3,2-dioxaphosphorinane derivatives 18 25, its non-occurrence being explained by the strong steric interaction between the cis-fused phosphate and cyclopentane rings. Accordingly, the cis phosphates (Y cis to H 1 ) 18a 23a and the trans isomers (X trans to H 1 ) 24b and 25b were demonstrated to populate almost exclusively the same C 1 conformation as observed for 3',5'-xylo-cAMP analogues [55] with OMe, OPh or Cl in the preferred axial orientation in 18a 23a, and with equatorial NMe 2 in 24b and 25b. At the same time, 18b 23b, 24a and 25a were reported to exist as C 1 B 2 [55], rather than T C 1 or C 1 B 1 equilibrium mixtures.…”

“…Accordingly, the cis phosphates (Y cis to H 1 ) 18a 23a and the trans isomers (X trans to H 1 ) 24b and 25b were demonstrated to populate almost exclusively the same C 1 conformation as observed for 3',5'-xylo-cAMP analogues [55] with OMe, OPh or Cl in the preferred axial orientation in 18a 23a, and with equatorial NMe 2 in 24b and 25b. At the same time, 18b 23b, 24a and 25a were reported to exist as C 1 B 2 [55], rather than T C 1 or C 1 B 1 equilibrium mixtures. However, conformation B 2 can become predominant for the epimeric pairs of D-ring-fused 1,3,2-dioxaphosphorinanes and also for their 1,3,2-oxazaphosphorinane analogues, where the five-membered ring D is part of a more rigid estrane framework.…”

“…Moreover, the chair-twist equilibrium has been shown to be solvent-sensitive. However, 2-oxo-1,3,2-dioxaphosphorinanes with cisannelated to a xylofuranose or cyclopentane ring, can adopt other conformational states [6,[51][52][53] due to the less strained arrangement of the fused rings [54,55]. The P-epimeric pairs of 5(R) and 5(S)-substituted P-OPh cyclic phosphates 14 17 with a cis-fused 1,2-O-isopropylidene--D-xylofuranose moiety, were synthesised in two steps from 11 by applying a one-pot hydrolysis-oxidation and Grignard reagent addition protocol and subsequent phosphorylation of the corresponding 1,3-diol precursors 12a c and 13a c [51] (Scheme 3).…”

Hydroxy group interactions in stannylated carbohydrates. Structures and thermal stabilities of 5-deoxy-5-C-(Ph3Sn)-1,2-O-isopropylidene-α-D-xylofuranose, 5-deoxy-5-C-(IPh2Sn)-1,2-O-isopropylidene-α-D- and -L-xylofuranose, and 5-deoxy-5-C-(I2PhSn)-1,2-O-isopropylidene-α-D- and -L-xylofuranose

“…The δ 119 Sn value [Ϫ107.3 ppm] and coupling constants, in particular J( 119 Sn-13 C ipso ) and J( 119 Sn- 28 The large 1 J( 119 Sn- The J(H 1 -H 2 ), J(H 2 -H 3 ) and J(H 3 -H 4 ) coupling constants, associated with the furanose rings, in 3-5 and 13 are in the same ranges reported for other 1,2-O-isopropylidene-α-xylofuranose derivatives. 31 While the changes from Ph 3 Sn to X n Ph 3 Ϫ n Sn at C-5 have no effect on these J(H-H) values, they do result in higher field shifts of H-1 and, to a lesser extent, of H-2, see Table 1. There are also changes to lower field for H-3.…”