Patent ID: 7683200

Claim:
A compound of formula (16): wherein: n is 0 or 1; R 1a is a C 1 -C 6 alkyl group, a C 3 -C 6 alkenyl group, a C 3 -C 6 alkynyl group, a phosphite oxygen protecting group, or a phosphate oxygen protecting group trimethylsilyl ether, triethylsilylether, triisopropylsilyl ether, t-butyldimethylsilyl ether, t-butyldiphenyl silyl ether, 2-trimethylsilylprop-2-enyl, 2-(trimethylsilyl)ethyl, or trimethylsilyl; in each occurrence of R 2a and R 2c , one of R 2a and R 2c is H and the other is selected from the group consisting of tert-butyloxycarbonyl (Boc), fluorenylmethyloxycarbonyl(Fmoc), 2,2,2-trichloroethoxycarbonyl (TROC), trimethylsilylethyloxycarbonyl (TMS-ethyloxycarbonyl), cyanoethyloxycarbonyl, allyloxycarbonyl, tetrachlorophthalimide, —C(O)OR x and —C(O)CH 2 C(O)R 6 ; or R 2a and R 2c taken together are a divalent nitrogen protecting group; R 4 is a C 5 -C 12 alkyl group or a C 5 -C 12 alkenyl group; R 5 and R 6 are independently a C 5 -C 15 alkyl group or a C 5 -C 15 alkenyl group; and Rx is a substituted or unsubstituted lower alkyl; or a salt thereof.