2-Dienol carbamates

Monodentate phosphoramidites, in particular (9) and its octahydro analogue, are found to be excellent ligands for the rhodium-catalysed asymmetric hydrogenation of aromatic enol acetates, enol carbamates, and 2-dienol carbamates with up to 98%... 

Attempts have been made to exploit the possibility of direct allylic oxidation of codeine with chromic acid,(253) Mn02,(254) and SeOz plus t-butyl hydroperoxide(255) to the corresponding 14-OH derivative, but each approach gave a low yield. Schwartz and Wallace 255 achieved a six-step transformation of codeine to a noroxycodone (52%) and noroxymorphone (43%) according to Scheme 2.20. Oxidation of the carbamate of norcodeine gave 166 (R = H), which was converted to the dienol acetate, 167. Subjection of this to... 

Schlessinger and coworkers have studied the aldol reactions of the dienolates derived from the vinylo-gous carbamate (18) in all cases, reaction occurs solely at the 7-position, as shown in equation (31). Various evidence has been adduced that (18) reacts kinetically at the 7-position, in contrast to the behavior of crotonate enolates (vide supra). The process has been used to synthesize the Prelog-Djerassi lactonic acid and a chiral version of (18) has been used to synthesize a fragment of the antibiotic virgi-niamycin M2 (vide infra). ... 

Moving forward from 59, six steps were required to convert this compound to 60. Vicinal dihydroxylation of the olefin was followed by oxidative cleavage of the intermediate diol using lead tetraacetate. Reductive amina-tion of the resulting aldehyde with methylamine, followed by acylation of the intermediate secondary amine gave the desired carbamate. Swern oxidation of the secondary alcohol, followed by enol ether formation gave 60. Elimination of -toluenesulfinic acid from 60 provided 61. Oxidation of this dienol ether to dienone 62 was followed by release of the secondary amine, followed by a conjugate addition reaction to establish the critical C-N bond. The remainder of the synthesis followed known chemistry. The mixture of enones 63 was converted to codeinone (35), codeine (3) and then morphine (1). 

Following assembly of the key C9-C11/C20 subunit, conjugated Z-dienol, the dimethyl acetal 20 was converted to the required carbamate in 33% yield over... 

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