PubMed:2073634 JSONTXT

{"project":"sentences","denotations":[{"id":"TextSentencer_T1","span":{"begin":0,"end":143},"obj":"Sentence"},{"id":"TextSentencer_T2","span":{"begin":144,"end":343},"obj":"Sentence"},{"id":"TextSentencer_T3","span":{"begin":344,"end":544},"obj":"Sentence"},{"id":"TextSentencer_T4","span":{"begin":545,"end":770},"obj":"Sentence"},{"id":"TextSentencer_T5","span":{"begin":771,"end":979},"obj":"Sentence"},{"id":"TextSentencer_T6","span":{"begin":980,"end":1249},"obj":"Sentence"},{"id":"TextSentencer_T7","span":{"begin":1250,"end":1436},"obj":"Sentence"},{"id":"TextSentencer_T8","span":{"begin":1437,"end":1565},"obj":"Sentence"},{"id":"T1","span":{"begin":0,"end":143},"obj":"Sentence"},{"id":"T2","span":{"begin":144,"end":343},"obj":"Sentence"},{"id":"T3","span":{"begin":344,"end":544},"obj":"Sentence"},{"id":"T4","span":{"begin":545,"end":770},"obj":"Sentence"},{"id":"T5","span":{"begin":771,"end":979},"obj":"Sentence"},{"id":"T6","span":{"begin":980,"end":1249},"obj":"Sentence"},{"id":"T7","span":{"begin":1250,"end":1436},"obj":"Sentence"},{"id":"T8","span":{"begin":1437,"end":1565},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"Etoposide: a new approach to the synthesis of 4-O-(2-amino-2-deoxy-4,6-O-ethylidene-beta-D-glucopyranosyl)-4'-O- demethyl-4-epipodophyllotoxin.\nSynthesis of 3-O-acetyl-2-benzyloxycarbonylamino-2-deoxy-4,6-O-ethylidene- alpha-(7 alpha) and-beta-D-glucopyranose (7 beta) and their 3-O-chloroacetyl analogues (11 alpha and 11 beta) are described. Condensation (BF3-etherate, ethyl acetate, -20 degrees) of 7 alpha with 4'-O-benzyloxycarbonyl-4'-O-demethyl-4-epipodophyllotoxin (8) afforded mainly the beta-glycoside 9 beta (alpha, beta-ratio 1:9). Condensation of 11 alpha beta with 8 or the 4'-O-chloroacetyl analogue 13 gave mainly the 4-O-(2-benzyloxycarbonylamino-3-O-chloroacetyl-2-deoxy-4,6-O-ethyl idene-beta-D- glucopyranosyl)-epipodophyllotoxin 12 beta or 15 beta. Glycosidation of podophyllotoxin (14) with 11 alpha beta (during which the aglycon epimerized at C-4 under the action of BF3-etherate) afforded alpha- (16 alpha) and beta-glycoside (16 beta) in the ratio 1:5. Removal of the chloroacetyl groups from 12 beta, its alpha analogue 12 alpha, and 15 beta gave the 4-O-(2-benzyloxycarbonylamino-2-deoxy-4,6-O-ethylidene-alpha-(17 alpha) and -beta-D-glucopyranosyl)-4'-O-demethyl-epipodophyllotoxins (17 beta and 20 beta), respectively. Hydrogenolysis of the benzyloxycarbonyl groups then gave 4-O-(2-amino-2-deoxy-4,6-O-ethylidene-alpha- (18 alpha) and -beta-D-glucopyranosyl)-4'-O-demethyl-4-epipodophyllotoxin (18 beta). Reductive alkylation of 18 beta and 18 alpha afforded the 2\"-deoxy-2\"-dimethylamino-etoposide 3 and its alpha analogue 19 alpha."}