Syntheses of Amino‐dideoxyallose and Amino‐deoxyribose Derivatives Using Acylnitroso Dienophiles

Abstract

Dedicated to Professor Elius J. Corey on the occasion of his 60th birthday (26.V11.88)The dimethyl acetals 4 of (E)-2,4-pentadienal and of (E,E)-and (E,Z)-2,4-hexadienals undergo regio-and stereospecific cycloaddition reactions with in-situ-generated acylnitroso dienophiles Sa and Sb, leading thereby to the corresponding dihydrooxazines 7a-d and 8c-d. cis-Glycolization of these latter adducts stereospecifically gave the dihydro derivatives 9a-d and 10d which, after sequential hydrogenolysis, deacetalization, and instant cyclization, led to the aminodeoxyribose derivatives 17a, 17f, and 18, and to the amino-dideoxyallose compounds 17c and 17b. These piperidino-deoxysugar derivatives exhibit a strong anomeric effect, i.e. OH-C( 1) is always axial, which is explained in terms of a n,(n)-o*(C-OH) orbital compression, as compared to the less pronounced one in the more classical pyranose series.

Synthesis of Amino‐L‐Lyxose Phosphonates as Fucosyl‐Phosphate Mimics

“…Scheme 2. The N-OH group is generally reduced by hydrogenolysis over Pd/C, [15,18] and even better in the presence of aqueous HCl. [16,17] We have verified that this reduction also occurred by hydrogenolysis over Raney-nickel [20] but not over 5 % Pd/ C alone. O,N-Bis-deprotection of 6a,b was finally carried out by hydrogenolysis with 5 % Pd/C in EtOH and aqueous 1  HCl to give in one step the pyrrolidine-phosphonates 7a,b as hydrochlorides.…”

Asymmetric synthesis of pentono‐ and 6‐deoxyhexono‐δ‐lactams via hetero‐Diels‐Alder reactions with nitroso dienophile

“…Carried out with the protected derivatives 5a, b, it gave easily the dihydroxy esters 6a, b and 7 in 65 -70 % overall yield. As observed with other sorbic-acid derivatives [23] [34], the disubstituted derivative 5b gave only one dihydroxy ester 6b; to the contrary, the monosubstituted derivative 5a yielded the two crystalline dihydroxy esters 6a and 7 in a 4 : l ratio which were easily separated by chromatography. In both cases, the two cis-arranged OH groups in the major dihydroxy esters 6a, b proved to be in trans-position with respect to the carboxylate group.…”

“…The (6R)-configuration for the monosubstituted adduct 4a and 5a was corroborated by comparison of the physical data of the final pentono-&lactams with those of the literature [26-291. The optical purity of the adducts 4a, b was determined by HPLC on chiral columns (Chiralpack A D or Chiralcel O D ) with their protected derivatives 5a, b, racemic (-k)-5a, b being used as references. These racemates were synthesized by Diels-Alder reaction of the acids 2a, b with acyl-nitroso dienophile BnO-CO-N=O (prepared by in situ oxidation of the corresponding hydroxamic acid with periodate salts in CH,Cl, [34]), followed by esterification with HCI/MeOH. Enantiomeric proportions for the monosubstituted adduct derivative 5a were found to be 93 : 7, corresponding to 86 YO enantiomeric excess (ee) which rose to 96% ee after one recrystallization of 4a.…”

Cascade Reactions. A Simple One‐pot Synthesis of the Mitomycin Skeleton

“…This is due to a strong steric interaction between Me-C(3) and the N-substituent in the other pseudochair conformation, a fact which we have already reported in [13]. Kresze and Fir1 have already assigned to the type 13 minor adduct (p-chlorophenyl instead of Ph at the N-atom) the inverse regioisomeric structure with respect to the one depicted in Scheme 2 [7].…”

“…The 'H-NMR spectra of the cycloadducts could be interpreted unambiguously, in particular by comparison with cycloadducts 12 and 13 [13] which were obtained by regiospecific Diels-Alder cycloadditions of the dimethyl acetals 14 (80%) and 15 (20%) with la. The dimethyl acetal 14 (E,E) gave the major adduct 12 (go%), while 15 (E,Z) gave the minor adduct 13 (20%; Scheme 2).…”