ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The addition of phosphite anions and of tris(trimethylsilyl) phosphite (P(OSiMe3)3) to N-glycosyl-C-arylnitrones was examined. While these nitrones proved inert towards the phosphite anions, they reacted with P(OSiMe3)3 under catalysis by Lewis acids. Thus, P(OSiMe3)3 reacted with the crystalline (Z)-N-glycosylnitrones 2 and 8 to give the optically active N-hydroxy-α-aminophosphonic acids 4 and 10, respectively, and hence the α-aminophosphonic acids 5 and 11 in yields up to 92% and with an enantiomeric excess (e.e.) up to 97% (Scheme 1). The absolute configuration of the phosphonates depend upon the nature and - in one case - upon the quantity of the catalyst (Figure). Upon catalysis by HCIO4 or Zn(OTF)2, p(OSiMe3)3 added to 2 to give, in both cases, the (+)-(R)-phenylphosphaglycine 5 (optical purity 79-84 and 90-93%, resp.). The optical purity (o.p.) was hardly influenced by the amount of these catalysts (0.02-;1 equiv.). However, catalysis by ZnCl2 gave, with trace quantities of the catalyst, (-)-(S)-5 (o.p. 79%), while an equimolar amount of ZnCl2 yielded (+)-(R)-5 (o.p. 82%). The HClO4-catalyzed addition of P(OSiMe3)3 to the nitrone 14 (Scheme 2) led to (+)-(R)-N-hydroxyphosphavaline 15 (78%) and hence to (-)-(R)-phosphavaline 16 (71% from 14 e.e. 95%). Under conditions leading from the nitrones 2, 8, 14, and 20 (Schemes 1 and 2) predominantly to (R)-α-aminophosphonic acids, the addition of P(OSiMe3)3 to nitrone 18, possessing a benzyloxy substituent as an additional potential ligand for the catalyst, gave (S)-phosphaserine 19. The addition of P(OSiMe3)3 to the nitrone 20, catalyzed by Zn(OTf)2, led to (+)-(R)-N-hydroxyphosphamehionine 21 (71%, e.e. 77%) and hence to (-)-(R)-phosphamethionine 22 (77% from 20, e.e. 79%). Catalysis by trace quantities of ZnCl2 gave (+)-(S)-22 (85%, e.e. 61%). The enantiomerically pure aminophosphonic acids 5, 11, and 16 were obtained by recrystalliztion. The e.e. of the N-hydroxyaminosphosphonic acids 10, 15, and 21 and the aminophosphonic acids 5, 11, 16, and 22 were determined by the HPLC analysis of the dimethyl N-naphthoyl-α-aminophosphonats 7, 13, 17, and 23, on a chiral stationary phase.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19870700603
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