| abstract |
The present invention relates to a compound of formula (6)n nwherein R is alkyl, aryl, arylalkyl, or heteroaryl, and wherein R 1 is -XR wherein nX is O, nS, or nSe, or R 1 isn nwherein R 2 or R 3 is independently nalkyl ncycloalkyl, narylalkyl, or naryl, or nR 2 and R 3 together are n-(CH 2 ) 4 -, n-(CH 2 ) 5 -, n-(CH(R 4 )-CH 2 ) 3 -, n-(CH(R 4 )-CH 2 ) 4 -, n-(CH(R 4 )-CH 2 ) 2 -(CH(R 4 ))-, n-(CH(R 4 )-CH 2 ) 3 -(CH(R 4 ))-, n-CH 2 -CH 2 -A-CH 2 -CH 2 -, n-CH(R 4 )-CH 2 -A-CH 2 CH 2 -, n-CH(R 4 )-CH 2 -A-CH 2 CH(R4)- nwherein R 4 is alkyl of from one to four carbon atoms, A is O, S, or N, and R is as defined above. |